Monday, September 4, 2017

Mosses of Central Florida 28. Climacium americanum

Photo courtesy Robert A. Klips, Ohio Moss and Lichen Association.
Climacium americanum Bridel (Climaciaceae) is a distinctive moss with a "tree-like" shape, and often of a yellow-green color.  It has upright stems that branch out into a number of spreading, leafy branches. It occurs in our area in wet habitats, most often on decaying logs in cypress swamps, but elsewhere in damp soil along rivers or marshy depressions.

In Florida, this species is distributed from the northern counties southward to Manatee County, with some records from Broward and Monroe counties.  It also occurs widely northward in the eastern U.S. and Canada, the Rocky Mountains,  Pacific Northwest, and Alaska.

The leaf has a distinct midrib, which tapers out just short of the leaf tip, jagged teeth in the upper part, a broad, spreading base without inflated cells, and cells that are "worm-like" (elongate,  tapered, and slightly wavy). Between the leaves are many branching, thread-like appendages called paraphyllia.

The broad leaf base and tapered tip of the leaf of Climacium americanum 
give it a triangular shape. Photo courtesy Robert A. Klips, Ohio Moss and
Lichen Association/
The spore capsules are erect, symmetrical, and narrowly cylindrical.

Although it was collected a number of times in our local Hillsborough River Basin in the 1970's, I have yet to find living specimens myself.  So I am grateful to Bob Klips of the Ohio Moss and Lichen Association for the use of his photos.
The worm-like cells of Climacium can be seen in this photo from Wikimedia
Commons of C. dendroides (not in our area). 

Thursday, August 24, 2017

Mosses of Central Florida 27. Dicranella hilariana

Dicranella hilariana (Montagne) Mitten (Dicranaceae) is typically found on moist, clay banks, but appears to have adapted also to the disturbed slopes of phosphate mine pits and may be partially covered with sand.  From the related genus Dicranum, Dicranella species differ mainly in their smaller size, shorter leaves, and lack of inflated (alar) cells at the base of the leaf. Like the other genera in this family, the leaf has a massive midrib, and the cells are squarish to rectangular.
Leaves of Dicranella hilariana have a thick midrib and square
to rectangular cells.
From the two other species of Dicranella occurring in central Florida, D. hilariana differs  primarily in the shape of its capsules, which are erect, symmetrical, and smooth, and in the color of the capsule stalks, which are yellow but may become somewhat reddish as they age. In D. varia the capsules are asymmetrical, somewhat bent to the side, and borne on red stalks. In D. heteromalla, the stalks are yellowish, but the capsules are nodding and  conspicuously furrowed.  
Found in a phosphate pit in Hillsborough County, this specimen of  Dicranella hilariana is partially
buried in the sand.  Note the symmetrical, smooth capsules and yellowish to reddish capsule stalks.  Latina 42 (USF)

Monday, August 21, 2017

Mosses of Central Florida 26. Dicranum condensatum

Dicranum condensatum Hedwig (Dicranaceae) grows in sandy soil throughout Florida, sometimes forming deep cushions made up of long, mostly dead stems and leaves, with green tips. The leaves along the stem are of the same size and shape and are produced indefinitely, in contrast with the related species Campylopus surinamensis.  It does produce spores, but apparently only rarely in our area.
A well-established clump of Dicranum condensatum nearly 6 cm deep.
Only the leaves in the top centimeter or so were alive when this specimen
collected ( Lassiter 2077, USF)
Leaf cells of  D. condensatum are squarish-rectangular in the
upper part, and the margins of the leaf are toothed. 

Like all members of the family, the midrib (costa) of the leaf is massive, but not as broad as in Campylopus, occupying only 1/10 to 1/5 the width of the  leaf in the lower part. Leaves are mostly 3.5-4.5 mm long, and more or less curled or twisted at their tips when dry.  Cells are angular squarish near the tip, becoming more elongate toward the base, and distinctly larger and empty at the base (alar cells).

Leaves are twisted-curled when dry.
Two other species of Dicranum are found in Florida, but not as common or widespread.  D. scoparium is found in humus, rotting stumps, tree bases, and has short-sinuous leaf cells. D. flagellare, found only in north Florida, has specialized whip-like branches with short, scale-like leaves pressed to the stem that arise from the axils of ordinary leaves. The related Dicranella has much shorter leaves.  Ditrichum pallidum (Ditrichaceae) is sometimes confused with Dicranum. It grows in similar habitats, but typically has much longer leaves on shorter stems, resembling tiny clumps of grass.

Tuesday, August 15, 2017

Mosses of Central Florida 25. Campylopus surinamensis

Campylopus surinamensis Müller Hal. (Dicranaceae) is a hardy, desiccation-tolerant moss found in the dry, sandy soil of the Pine Flatwoods and dry roadsides.  Synonyms include C. donnelli and C. gracilicaulis.  From other members of its family, it is typically distinguished by the habit of producing shoots with two forms of leaves.  Along the lower parts of the shoot, the leaves are small, widely spaced and pressed against the stem. In the upper part of the shoot, leaves are longer, and crowded into a distinct tuft.  It apparently does not produce spores anywhere in North America, but reproduces asexually by means of small, hooked leaves produced in the axils of the main leaves.
As a colony of Campylopus surinamensis develops, some shoots form as short rosettes, but later shoots elevate their rosettes atop sparsely foliated stems. Photo of Essig 20090209-1 (USF)

The leaves are dominated by the massive midribs, that occupy about a third or more of the leaf width at the base, and nearly all of the leaf in the middle and upward into the prolonged tip.  Other members of the family have still massive, but narrower, midribs, occupying less than a third of the leaf width at the base.  The upper parts of the leaves are toothed along the margins. Leaf cells in the narrow blade region are squarish to irregular, becoming larger and more rectangular at the base. Leaves are somewhat curved but stiff when dry, not curled.
The leaves of Campylopus species are dominated by their massive midribs.

Tuesday, August 8, 2017

Families Matter

You probably remember from introductory biology course, that the official way of naming a species is the binomial ("two-name") system. Each species name is composed of the genus name and the specific epithet.   For example, Quercus alba is the name for the white oak.  Quercus is the genus, which contains a number of other species of oaks, and alba is the specific epithet that refers exclusively to this one species.

In almost all scientific communication and labeling practices, however, a third identification tag, the family name, is added - e.g. Quercus alba (Fagaceae). This greatly increases the utility and comprehensibility of the naming system.

The binomial system itself evolved from a fundamental human instinct to recognize categories of things, and specific types within those categories. Before Linnaeus established the formalized latin system that gave us Quercus alba, there were "white oaks, red oaks, etc. (and the equivalent in various other languages), just as there  were John Smith, William Smith, etc. Referring to just a "white" or "John," or "William," doesn't tell us much at all.

The  binomial gives some context to a name, and helps us interpret new information.  If someone describes a new species, Quercus antarctica (hypothetical) for example, we immediately know that it is another species of oak.  We can predict that it will be a woody tree or shrub with simple leaves, and that it produces acorns. The family name adds another layer of recognition and predictiveness.

Suppose, for example, someone comes into the room raving about the spectacular specimen of Trigonobalanus doichangensis she'd seen at a botanical garden in Singapore.  I myself would have stared blankly at her, having no idea what that gibberish stood for.  But then she tells me that Trigonobalanus is a genus in the family Fagaceae.  A big light bulb turns on in my head. Fagaceae is the family to which Quercus belongs, along with Castanea (chestnuts), Fagus (beeches), and several other genera. Suddenly I have an approximate idea of what this plant is.

The family name is therefore extremely valuable for recognizing, characterizing, identifying, labeling, storing, retrieving, and providing relationship context for plant specimens. Sometimes it is of more value than the genus name for providing a rough idea of what a plant is and where it fits in relationship to other plants, as in the Trigonobalanus example above. This requires, of course, some knowledge of plant families. Learning the characteristics of families is a routine part of studying plant taxonomy, but will also be highly useful to anyone with an interest in plants.  Even the use of common names like "the orchid family" or the "iris family," etc., will be helpful when communicating with a lay audience.

The taxonomic system is a hierarchy of taxonomic categories, or taxa. Genus and family are two levels of taxa.  Theoretically, we could also append the names of higher categories, like orders, classes, phyla, etc. You will find those in textbooks, but for everyday use, they would amount to information overload. We can refer casually to important higher categories, like angiosperms, gymnosperms, green algae, etc., without really worrying about their technical names or their rank (their level within the hierarchy).

In this botanical garden label, the binomial, Galium odoratum, is most prominent.  Much additional useful information is also included, but most importantly, the family name, Rubiaceae, is included, in this case at the top left.  Incidentally, purists will point out that the binomial, by convention should be italicized, but that is not always possible.  Often, the machines that make labels do not have an italic font capability.  In fact, the formatting tools for the host service under which this blog is created does not allow for italics in the title, as can be seen in my posts on moss genera.
Photo copyright Oxford University, fair use. 

Familly names for plants have been standardized with the "aceae" ending, which is attached to the name of the first named genus in the family  The Asteraceae (sunflowers, etc.) gets its name from the genus Aster.  So you'll know when you're seeing a family name.  Some older names were different, ending in "ae,"  and using a descriptive term instead of a genus name as the base.  The old name for the Asteraceae was the "Compositae," referring to the composite or compound nature of the flower heads.  You will still see these type of names in the older literature.  Some of the other common ones are "Palmae" (for Arecaceae), "Gramineae" (for Poaceae), "Leguminosae" (for Fabaceae), "Labiatae" (for Lamiaceae), "Crucferae" (for Brassicaceae) and "Umbelliferae" (for Apiaceae).

The point(s) of these remarks are several:

1. For botany instructors and students, learning the characteristics of the plant families that occur in your area, and using plant family names when labeling or referencing specimens, has a huge practical value.

2. When identifying plants, recognizing the family narrows down your search and allows you to skip over what is usually the most difficult part of a taxonomic key.

3. Referencing the plant family when writing or talking about plants puts them into a context of relationship.  The taxonomic system is not an arbitrary set of names, but reflects the natural evolutionary relationships among plants.

4. For practicing taxonomists, we need to keep in mind the practical value of maintaining a manageable number of stable families with meaningful, recognizable, distinguishing characteristics. That's not always easy, given the directive of modern phylogenetic taxonomy to reorganize plant diversity into strictly monophyletic taxa, which often requires splitting of old familiar families into smaller units, or lumping familiar families into larger families with more diverse characteristics.  

Thursday, July 20, 2017

Mosses of Central Florida 24. Anomodon minor

Anomodon minor has creeping  primary stems with short, scale-like leaves
and semi-erect branches with larger, tongue-shaped leaves. Photo from dried
herbarium specimen: Merner s.n. 15 June 1979 (USF)
Anomodon minor (Hedwig) Lindberg (Anomodontaceae) is a creeping moss occurring on bark at the bases of trees.  It is distributed widely in North America, extending south to Hillsborough and Polk Counties in central Florida. It has
Capsules of Anomodon minor are erect (unbent) and symmetrical.
Photo courtesy Robert A. Klips, Ohio Moss and Lichen Association.
two orders of leafy stems.  The primary stems creep horizontally along the substrate, and bear relatively short, scale-like leaves, while branch stems are semi-erect to spreading, with larger, tongue-shaped leaves. Branch leaves are broadly rounded at the tip with a short, hard point, have a distinct midrib, and the cells are small, roundish, and papillate (with hard, translucent bumps). When dry, the leaves fold against the stem. Capsules are erect and essentially symmetrical.  In habit and leaves, it somewhat resembles members of the Thuidiaceae, into which this genus is sometimes placed, but in that family, primary stem leaves are larger than the scale-like branch leaves, in both types of stems there are leaf-like paraphyllia between the true leaves, and capsules are asymmetric and bent to the side.

Within the Anomodontaceae, Anomodon is distinguished from the only other genus, Herpetineuron, by the shape and other features of the leaves. In Herpetineuron, leaves gradually taper to a point and the cells are smooth, without papillae.  Three other species of Anomodon occur in Florida.  A. tristis appears to form thinner mats, occurs higher up on tree trunks, and is found only in the northern part of the state. A. attenuatus forms denser mats, with more frequently branched stems that lay more-or-less flat, and taper at the ends with increasingly smaller leaves.  In A. rostratus, leaves are long and taper to a fine, hair-like point.
Leaves of Anomodon minor are elongate, tongue-shaped and with a rounded
tip with small hard point. Cells are tiny, roundish and equipped with papillae.
Lighter streak in the center is the midrib. 

Thursday, July 6, 2017

Mosses of Central Florida 23. Hygroamblystegium varium

Hygroamblystegium varium (Hedw.) Mönk.(Amblystegiaceae) is another moss frequently found in aquatic habitats in central Florida, along with Leptodictyum, Fontinalis, and species of Fissidens. Its leaves are shorter and spread more 3-dimensionally around the stem than those in Lepidodictyum, and the stems branch more frequently. Fontinalis is easily distinguished from these genera as its leaves lack a midrib altogether. The leaf cells in Fontinalis are also more elongate and curved, and the stalks of the sporangia (capsules) are extremely short.  Fissidens, of course, is easily recognized by the smaller secondary leaves attached at each node with the main leaves.  Like Amblystegium and Leptodictyum, which are in the same family, the capsules of Hygroamblystegium are erect, but slightly curved, and arise from short stems along the creeping main stems.
Compared to the related genus, Leptodictyum, the stems branch more frequently in Hygroamblystegium, and the leaves
are shorter, more scale-like, and distributed 3-dimensionally around the stem.  The capsule is upright, but slightly curved and asymmetric.  From a dried specimen, Wagner-Merner s.n., 17 May 1969 (USF).

Leaf cells of Hygroamblystegium are short-rectangular or sometimes
more elongate.
The family Amblystegiaceae is one of many moss families in taxonomic flux.  Even the treatment in Flora North America (FNA) is self-proclaimed to be tentative, with the treatment of genera and species still controversial and unsettled. Hygroamblystegium and Amblystegium, each containing only one recognixed species, are weakly separated, and sometimes combined into a single genus. The principal differences noted in FNA are that the leaves of Amblystegium are smaller than those of Hygroamblystegium and the midrib is weaker, and that the plants lack paraphyllia (extra leaf-like or thread-like appendages between leaves).  Amblystegium is also said to be always terrestrial, while Hygroamblystegium is often (but not always!) aquatic.  By this definition it appears that Amblystegium serpens is found only in north Florida, and reports from central Florida need to be investigated.

A lucky shot of the tip of the capsule of Hygroamblystegium varium.
In herbaria, Hygroamblystegium varium is more likely to be filed under Amblystegium, and it might be best to leave them there until the taxonomic dust settles. Some other species have been recognized, including Hygroamblystegium tenax, H. fluviatale, H. humile, H. trichopodium, and H. noterophilum, but it seems clear that these are all just variants of  the aptly named H. varium.

Friday, May 19, 2017

Mosses of Central Florida 22. Leptodictyum riparium

Leptodictyum riparium (Hedw.) Warnst. (Amblystegiaceae) is the most common aquatic moss in central Florida.  It is commonly found growing submerged on rocks along rivers, typically in thick mats, or exposed on rocks or tree bases close to water.  Other aquatic mosses include some forms of Hygroamblystegium varium, and two species of Fissidens, which are much less common.  Aquatic species of Sphagnum are confined to north Florida.  Amblystegium serpens may be in our area, but voucher specimens need to be verified.
Leptodictyum occurs in thick underwater mats. The stems are long, straight and sparsely branched.  The leaves are spread stiffly in one plane, even when dry.  From Franck 3314 (USF).

Leptodictyon is distinguished from other aquatic mosses by its long, straight, sparsely branched stems, with leaves extending stiffly from the sides of the stem (in more or less one plane). The leaves remain more or less stiff when dry, by may be somewhat rumpled.  It rarely produces sporophytes in our area.   Hygroamblystegium has shorter, more branched stems that tend to be more curved when dry, and shorter, more triangular leaves distributed uniformly around the stem.  It is also more often found with sporophytes.   Species of Fissidens are distinguished by their doubled leaves.
The leaves of Leptodictum have a distinct midrib, but which
does not quite reach the tip. From Franck 3314 (USF)

The leaves have a distinct midrib, and the leaf cells are generally elongate with thin, inconspicuous walls. Sporangia, when present, are somewhat curved and asymmetric, but none have been found among the specimens at USF.
The leaf cells are somewhat elongate and tapered at the ends,
but do not stand out sharply under the microscope. From
Lassiter et al 559 (USF)

Saturday, April 29, 2017

Mosses of Central Florida 21. Introduction to the genus Fissidens and F. pallidinervis

An image of Fissidens taxifolius illustrating the basic flattened shoot structure
 of the genus, with doubled leaf.  Image by Ralf Wagner.
According to Flora North America, twenty species of the genus Fissidens  occur in Florida.  By definition all members of this genus have a peculiar flattened leafy shoot with double leaves.  At each node or insertion point along the stem there is a full-sized leaf and a smaller leaf. The leaves are attached sideways to the stem, creating a flat, frond- or feather-like shoot. The leaves do, however, tend to curl when dry. At the bottom of this post is my effort at a simplified, short-cut key to the species.

As in most large moss genera, the individual species are distinguished by technical characters, mostly microscopic features of the foliage, and can only be definitively identified by experts.  However, there are some shortcuts that can help narrow down the choices in the relatively small number of species found in Florida (there are 450 species world-wide, 37 in North America), including the habit and length of the capsule stalks.

A dried specimen of Fissidens pallidinervis in the
herbarium at USF.  Note the relatively short stalks
of the capsules (sporangia), and the twisted  dry
Fissidens pallidinervis Mitten is relatively common in Florida, from the panhandle to the keys.  It is documented elsewhere only in Louisiana, but might be expected to show up in southern Georgia, Alabama, and Mississippi.  It typically occurs in moist areas at the bases of trees or on decaying logs, but found in our area also on shell mounds.

 From the other 19 species it is distinguished by a combination of  details, mostly of the leaves.  The cells of the leaf, on either side of the prominent midrib, are tiny, roundish and papillate, which means they bear small, translucent bumps on their surface.  This species has 2 or more such bumps, while some species have only one, and others have none (are completely smooth).

A single shoot from the specimen above.  Note that three
sporangia are rising from a single point on the stem.
The leaf cells of  Fissidens are small and roundish.  In this view,
the papillae can be detected as tiny bright spots of lighter
The shoots are tiny, about _mm long, and each may produce 2 or more sporangia near the shoot tip.  The stalks of the sporangia are relatively short, compared to other members of the genus, about 2 mm long. Only F. leptophyllus is in the same range, but in that species there is a clear limbidium ( a row of scleried-like cells) on the lower margin of the leaf, the leaf cells bear only 1 papilla, or are only rounded.  While others are variable, with stalks sometimes in this range, they are usually longer.

Provisional short-cut key to the species of Fissidens in Florida.

2_Sporangium stalks .5-.6mm………….F. fontanus
2_Sporangium stalks .7-1.5 mm……….F. hallianus
3_Sporangium stalks less than 6 mm long
        4_Occurring on bark, tree bases, not soil-specific
                   5_Sporangium stalks to 2 mm long
                         6_Leaf cells rounded or with one papilla; bases of trees, cypress swamps
                                                       …………………..............……..F. leptophyllus 
                         6_Leaf cells with several small papillae; bases of trees.....…F. pallidinervis 
                   5_Sporangium stalks 3.5-5 mm long
                        7_Leaf cells smooth to 1 papillate
                              8_Leaves up to 6 pairs, markedly toothed, cells 1-papillate; on bark,                                                                     logs, cypress trees…....F. serratus 
                           8_Leaves up to 25 pairs, not toothed, cells smooth to rounded; Bark, tree                                                             bases, rotten wood .................….F. santa-clarenis 
                              8_Leaves up to 10 pairs, minutely toothed, leaf cells smooth to bulging;                                                               bases of trees, soil............................…....... F. amoenus 
                      7_Leaf cells with several small papillae; leaf apex ending in a sharp, clear                                                               cell, on soil, banks, roadsides,  uprooted trees …….F. elegans
           4_Occurring on calcareous soil or rocks
                    9_ Found throughout Florida 
                            10_ occurring primarily at bases of trees; leaves in a pinnate pattern, up to 28 pairs
                                    ..........................................F. subbasilaris              
                            10_ on moist limestone in ravines; Leaves in a palmate pattern, up to 12 pairs .
                                    ......................................................F. zollingeri 
                    9_Found in north Florida only; on wet soil or rocks along streams, 
                            11_ Found in Florida panhandle *;soil, rocks and stones in shaded  ravines                                                               ………......................................................……..………..F. pellucidus 
                           11_Found in northern peninsular Florida, stems branched,........F. obtusifolius
                          11_Found in northern peninsular Florida*, stems unbranched …F. minutulus 
3_Sporangium stalks to 10-11 mm long
                            12_Capsules somewhat asymmetric, 1 mm long; occurring on bare, often clay, soil 
                                  .......................................................................................….. F. bushii 
                            12_Capsule 1.8 mm long; occurring at bases of trees, roots…......... F. dubius 
                            12_ Capsules symmetric; bases of trees, soil, logs .................…….F. bryoides 
3_Sporangium stalks to 15 mm long
                          13_ Capsules to 2.5 mm long, symmetric; on calcareous soil, north Florida only
                                                  ................................………………..F. polypodioides 
                          13_ Capsules to 1.5 mm long, asymmetric; seeps, moist rocks, soil;  central Florida
       3_Sporangium stalks to 25 mm; on seeps and rocks with dripping water……….. F. adianthoides 
       3_Sporangium stalks to 17 mm; on moist soil .humus, .rocks ................................…….. F. taxifolius 

*Questionable records of F. pellucidus and F. minutulus in Collier County, far removed from their north Florida ranges

Saturday, March 11, 2017

Mosses of Central Florida 20. Polytrichum commune

[For other mosses in this series, see the Table of Contents]

Polytrichum commune Hedwig (Polytrichaceae) is the giant among Florida mosses, with stems up to 10 cm. long. The stems are upright, with numerous stiff, narrow leaves.  It is not common in Central Florida, but when  found,  it is usually in extensive, dense colonies.
A colony of Polytrichum commune growing near Ft. Lonesome, Florida, in
Hillsborough County.  Many of the shoots in this picture bear clusters of sperm-producing antheridia at their tips. Photo by Steve Dickman.
There are seven species of Polytrichum found in North America, out of 70 worldwide.  P. commune is found throughout North America, Eurasia, New Zealand and Australia.  I recently found it in Taiwan.

The single specimen with sporangia at USF
shows the impressive dimensions of
Polytrichum commune. It comes from
northern Florida.
The leaves in the Polytrichaceae are unusual in consisting mostly of a massive midrib covered with vertical sheets of tissue arising from the upper surface.  This makes viewing the leaf anatomy more difficult, but the edges of the leaf in Polytrichum commune are lined with distinctive sharp teeth.  The bases of the leaves flare out into a broad sheath, and only here can one see the shapes of the cells.

 The upper surface of a Polytrichum leaf is covered with vertical,
blade-like sheets of tissue, here seen in cross section.
Photograph by Kristian Peters; Creative Commons
Attribution-Share Alike 3.0"
The midrib of Polytrichum commune is thick and fills the entire
blade.  Distinctive hard teeth line the edges.

The base of the leaf flares out into a thin
sheath, where the cells can be seen to be quite
narrow and elongate.

Evidently, Polytrichum commune rarely produces sporangia in Central Florida, as we have   We have o such specimens in the USF herbarium.  I can only speculate on the reasons for this.  In order for sporangia to form, sperm cells must swim from the tip of a stem where they are produced to the tip of a stem where eggs are being produced.  The large size of Polytrichum commune would make the conditions where this process could take place rather rare, particularly in the relatively hot and dry climate of Central Florida.  The species is at it's southern limit here. The one specimen with sporangia I've seen was collected in northern Florida.

 In addition, the colonies of Polytrichum are unisexual - they produce either sperm or egg, so two colonies of different sex must intermingle for sexual reproduction and spore-formation to take place.  The size of the plants would add to the difficulty of such mingling, and it is possible that some colonies in our area were established by a single spore, and hence unisexual.  In the photo  of living plants in Hillsborough County above, the colony appears to be all male.

Incidentally, in the process of researching this species, I found another excellent blog site for mosses from the University of British Columbia. Check it out for general information about the different groups of mosses.

Wednesday, March 8, 2017

The nearly forgotten art of comparative plant anatomy 1. Wood

The study of human anatomy is an obviously essential subject for all medical students, and most of us  have a basic idea of where our liver, lungs, large intestine, etc. are located - important information for identifying and fixing health problems.

Comparative anatomy, on the other hand, is about the differences and relationships among different organisms.  Most of what we know about dinosaurs comes from their bones.  Dinosaurs with bones of similar shape and arrangement are considered closely related to one another, and so we can reconstruct not only individual dinosaurs from their bones, but also phylogenies (family trees) and classifications.  Bones, by certain structural characteristics can also give us clues about what dinosaurs ate and whether they were warm-blooded or cold-blooded.

The comparative anatomy of plants has been put to similar use, helping us to interpret fossils, as well as to help identify and classify living plants.  Wood anatomists can identify the genus, and often the species, of a particular wood sample, and this is put to use by archaeologists and forensic scientists as well. How often has Abby from the hit TV show NCIS led her colleagues to a crime scene in the woods, by identifying wood, leaf, or pollen fragments from a murder victim's body or clothing?  Wood scientists, like those at the USDA's Center for Wood Anatomy Research, maintain a library of wood samples, including thin sections for microscopic examination.

The academic study of plant anatomy has, however, been in decline for decades (see Dengler 2002) .  This is partly because of the decline in botany courses in general, but also because of the need to make room in biology curricula for the massive amount of new material in ecology, cell biology, genetics, DNA sequencing, genomics, etc.  Plant anatomy in particular is considered by many to be old-fashioned, having largely been "done" in the 19th and early 20th centuries.  The study of plant anatomy, traditionally taught by looking through microscopes at prepared slides and making drawings, is admittedly tedious, requiring an interest and passion that is rare among most modern students.  To be of any use, one must acquire a broad knowledge of the different cell types and tissues of plants, and to recognize them as they vary in form from one species to another.  So it is a type of training, involving "memorization" of terminology and structural detail that is incompatible with the emphases on principles, theory, and experimental methodology in modern biology courses.  Moreover, the specialized equipment and skilled personnel for making thin microscope slides is rarely found anymore in biology departments.

Yet there is so much that we can learn still by comparing the anatomical structure of different kinds of plants.   Aside from practical applications in forestry, forensics and archaeology, it is still important in understanding the relationships and adaptations of plants in general.  The next few postings will illustrate some of this.

Let's start with the obvious: the structure of wood.  We will note first that plants are simpler that animals, and in plant anatomy, we're talking more about tissues than organs, actually more about what they would call histology in animal studies.  A tree trunk, composed of wood and other tissues is a single organ, so it is the different layers of tissues and cell types that determine how it functions, how it is adapted for its environment, and how one species differs from another.

True wood, as found in gymnosperm and dicotyledonous trees, consists of layers of xylem tissue added each year that increase the thickness of the trunk, branches, and roots.  Each layer is made up of water-conducting cells, and various sorts of supportive cells ranging from thin-walled parenchyma to thick-walled fibers.

The wood of  balsa (Ochroma pyramidale) is soft and light because the supportive
tissue around the large vessels is thin-walled.
 Photo from  Curtis, Lersten, and Nowak, University of Wisconsin, Stevens Point.

As an extreme example, the wood of the balsa tree is radically different from from that of a
teak tree, allowing us to not only recognize each under the microscope, but also telling us something about their different life styles.  Balsa is a fast-growing, short-lived tree that colonizes disturbed areas in forests and then gives way to longer-lived trees with more durable wood like mahogany or teak.  The density of wood is determined primarily by the abundance and distribution of fibers around the thinner-walled water conducting cell.  Durability is also enhanced by preservative chemicals secreted into the wood.
Among the great variety of dicotyledonous trees, there is great variety in the shape, arrangement, and abundance of these different kinds of cells. This variation has resulted in some woods being superior for fine cabinetry, others for resilient baseball bats (ash), durable bowling pins (hard rock maple), or strong shovel handles (hickory or ash). The wood database contains extensive images and data concerning the characteristics and uses of different kinds of wood.

In the tropical hardwood teak (Tectona grandis), the supporting tissue around the large vessels is made up mostly 
of narrow, thick-walled fibers.

In temperate trees, such as this red maple (Acer rubrum) the annual growth rings of wood
(horizontal bands) are marked by distinct boundary layer of smaller, thick-walled cells laid down in the Fall,
something you don't see in tropical woods.  The vertical bands of cells are made up of living
parenchyma cells, often with thick secondary walls.
The flexible woody stems of grape vine (Vitis spp.) contain exceptionally wide
rays of parenchyma tissue that separate the narrow wedges of vessels and other
supportive tissues.
The simpler, softer wood of conifers, like pine or fir, consists mostlyof a single type of relatively narrow cell, the tracheid, which combines strength with water-conducting ability.  As angiosperm trees diversified, ancient tracheids diverged evolutionarily into two kinds of cells. Strength and density functions were taken on as some cells developed thicker walls, becoming fibers.  Water-conduction was focused in other cells that remained thin-walled, but became wider, and shorter: the  stacked cylindrical cells of the vessels.  There is also a network of parenchyma cells that permeate the wood as flat rays or vertical strands
The wood of conifers in general is very simple, consisting mostly of  tracheids, which conduct water as well as provide
structural support for the tree.  The band of narrower, thick-walled cells running across the bottom of the image is a
boundary layer, marking the slowing and  cessation of growth in the Fall.  Above it, the uniform mass of cells produced
in the Spring and Summer.  

In pines and some other conifers, the uniform growth of
cells is interrupted by large resin canals.

In monocots, the ability to produce layers of wood was abandoned as their ancestors evolved underground stems and clonal lifestyles.  When some of them became trees again, as in palms or bamboos, their water-conducting cells remained in separate vascular bundles scattered throughout the interior of the stem and surrounded by dense sheaths of fibers.
The dense, wood-like property of a palm trunk is provided by dense masses
of fibers, not layers of xylem laid down in rings. In this preparation, the walls
of the fibers are stained green rather than the usual red.
The rigid wall of a hollow bamboo stem is filled with  fibrous bundles.

On-line wood anatomy resources:

Curtis, Lersten, and Nowak, Photographic Atlas of Plant Anatomy, revised 2015

Schoch,W., Heller,I., Schweingruber,F.H., Kienast,F., 2004:  Wood anatomy of central European Species.

Meier, Eric,  The Wood Database.

Inside Wood, North Carolina State University, developed by Elizabeth Wheeler and others.  This site is more technical, and contains the most extensive library of wood anatomy images.

Thursday, March 2, 2017

Special Announcement - Botany bill in US Congress

Americans - A rare bipartisan effort to support botanical research needs the support of your Congressional representative and Senators.

This is not the party vs party politics we're all so tired of.  This is about Americans who care about the environment and biodiversity working together to make a better world for future generations.  Contact your representatives to urge support of this bill.  

Below is the full announcement from the Botanical Society of America:

ACTION ALERT: Co-sponsors needed for H.R. 1054 - The Botanical Sciences and Native Plant Materials Research, Restoration and Promotion Act
We are thrilled to announce that The Botanical Sciences and Native Plant Materials Research, Restoration and Promotion Act (aka the “Botany Bill”; bill number H.R. 1054) was introduced by Representative Quigley (D-IL) and co-sponsor Ros-Lehtinen (R-FL) last week! 
Background info: Read the official Billsummary of the main points, and the press release about the Bill from Representative Quigley. To-date, 62 professional organizations have endorsed the bill. Updates on the progress of the Bill can be found on the Plant Conservation Alliance Resources page. You can also track the Bill’s progress here.
We need your help!
Now that the Bill has been formally introduced, additional co-sponsors on both sides of the aisle are being sought. If you support the Bill, AIBS asks that you please call your representatives and voice your support for H.R. 1054 AND ask your representative to co-sponsor the Bill. Bi-partisan support will be required for the Bill to be introduced on the floor of the House of Representatives
How to prepare for your call/meeting
The following links provide information to help you prepare for your call/meeting with your Representative.
  1. Talking points on botanical science and native plant issues
  2. Summary of relevant funding language in the Department of the Interior Appropriations Bill 2017 (refer to talking points above for more information).
  3. Tips on meeting with a legislator or member of staff
Note that there is no companion legislation in the Senate yet.
If you have any suggestions for members of the House of Representatives that may be interested in co-sponsoring, or if you would be willing to reach out to your representative directly to let them know about this legislation and ask them to become a co-sponsor, please contact

Find an easy way to take action through the AIBS Legislative Action Center where you just enter your zip code to contact your representative about this Bill.
BSA Office
4475 Castleman Ave.
St. Louis, Missouri 63110
PH 314-577-9566, FAX 314-577-9515
American Journal of Botany -
Applications in Plant Sciences -
Plant Science Bulletin -
Botany Conference -

Sunday, February 19, 2017

Mosses of Central Florida 19. Rosulabryum capillare and R. pseudocapillare

Although the leafy shoots are buried within a
different moss, the presence of this Rosulabryum
is evident by the abundant and very large sporangia,
or capsules.
[For other mosses in this series, see the Table of Contents]

Like many other groups of mosses, those in the family Bryaceae are difficult to identify.  The available keys are highly technical and difficult to for non-specialists to follow.  The two species of Rosulabryum are presented together here because of those difficulties. R. capillare (Hedwig) J. R. Spence (Bryaceae) is common throughout North America, including Canada and our western states.  According to Flora North America, it is not found in Florida, but the related species R. pseudocapillare (Besch.) Ochyra takes its place.  However, numerous collections made in Florida have been identified by experts as R. capillare, along with many labeled as R. pseudocapillare.

Here, some leafy shoots have been isolated.
They are upright and radially symmetrical,
and the stalks of the sporangia arise from
the bases of the shoots. Sporangia are
symmetrical, cylindric and nodding.
Rosulabryum pseudocapillare typically has numerous thread-like reproductive structures (filiform gemmae) in the upper leaf axils, at least when not producing sporangia, while those of R. capillare do not.

Rosulabryum is common in Central Florida  and produces abundant nodding, nearly cylindrical sporangia (capsules) in the springtime.  It can be found most readily in wet soil at the margins of receding ponds, forming mounds of upright stems. It might almost be considered weedy, as it also pops up readily in pots containing wet, organic soil, and in wet soil along sidewalks.

Rosulabryum was formerly included in the genus Bryum, having been segregated out on details that are hard to follow in the formal keys.  In Florida, only Bryum argenteum remains in the original genus, which incidentally gives its name to the entire clade of non-vascular plants we call Bryophytes.  B. argenteum differs from Rosulabryum in its more compact growth form, its grayish coloration, and leaves that press flat against the stem when dry.  The dried leaves of Rosulabryum twist around the stem.

Nearly ripe sporangia of Rosulabryum
are cylindrical and bright green.
The leaves of Rosulabryum become twisted when dry.
The other segregate from Bryum found in Florida is Gemmabryum, but it apparently forms sporangia less often than Rosulabryum, relying more on asexual bulbils and gemmae for reproduction.  When sporangia do appear, they are more egg- or pear-shaped.  The leaves in Gemmabryum are also said to be pressed flat against the stem when dry, as in Bryum argenteum, rather than being twisted like in Rosulabryum.

Leaves of Rosulabryum, like other members
of the famly, have a strong midrib (or costa).
Leaves in the Bryaceae have a strong midrib, and the leaf cells are mostly large, more-or-less rectangular or rhomboidal in shape, thin-walled, and with numerous distinct chloroplasts.  This, along with the upright, mound-forming stems and the nodding sporangia, makes members of the family fairly easy to recognize, though the genera and species are more difficult to distinguish.

Leaf cells of Rosulabryum, are thin-willed,
revealing many distinct chloroplasts within.

The leafy shoots of Rosulabryum peudocapillare produce
many thread like reproductive structures called filiform gemmae,
while those of R. capillare rarely do.