Wednesday, November 1, 2017

Mosses of Central Florida 36. Weissia controversa

A colony of Weissia controversa growing as a low cushion
on landscape fabric around a live oak tree on the campus of
the University of South Florida in Tampa.
Weissia controversa Hedwig (Pottiaceae) is a rosette moss, (i.e. with upright,
short-stemmed shoots, with leaves in a circular arrangement, like a rose), that forms extensive colonies on disturbed soil or sometimes rocks.  The leaves are elongate with a strong midrib that extends beyond the tip in a sharp point.  It is most distinctive in the margins of the leaves that roll tightly inward onto the upper surface (involute). 

The margins of  the long, narrow leaves of
Weissia spp. are distinctively rolled over
the upper surface.
Leaf cells are small, roundish, and papillose (with small, forking bumps), except at the base, where they are larger, rectangular and clear.
Leaf cells are compact, roughly circular, on ether side of the
prominent midrib.

Spore capsules are upright, symmetrical, goblet-shaped, dark brown when mature, and elevated on stalks up to .8 cm in length.
The spore capsules of Weissia controversa are dark brown at maturity, and broadest at the top, like a wine goblet. Most of the capsule here, however, are still topped by their short, beaked lids, or opercula, and some by the outer green sheathes (calyptras).

Weissia controversa is found in nearly every state and province in North America, including Greenland, and in Florida it has been well collected south to Manatee and St. Lucie Counties, but also with reports from Miami-Dade County.

Weissia jamaicensis (Mitten) Grout is a related species, with a more tropical and warm-temperate distribution, found in Florida, Georgia, westward to New Mexico, and north to Missouri, but  not in the Carolinas.  In Florida, it appears to overlap the distribution of W. controversa, but has been much more sparsely collected.  It differs in that the tip of the leaf is usually hood-like, and the base of the leaf flares out into broad shoulders.

Weissia ludoviciana and W. muehlenbergiana  are found throughout eastern N. America and in north Florida.

From other genera in the Pottiaceae, aside from the involute margins, Weissia species differ in their long, narrow leaves. Tortella species are somewhat similar, but not distinctly involute along their margins except sometimes at the tips.  Tortella also differs in the distinct V-shaped region of large, clear cells at the base of the leaf.

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