Monday, October 23, 2017

Mosses of Central Florida 34. Callicostella pallida

The branching leafy shoots of Callicostella pallida adhere closely to this piece
of decaying wood. Photos from Lassiter 2028 and 2029 (USF).
Callicostella pallida (Hornschuch) Ångström (Pilotrichaceae) is a small, creeping moss found on tree
bases, exposed roots, rotting logs, limestone, and occasionally on submerged rocks, often in deep shade. The indefinite, branching leafy shoots cling closely to their substrate. The ovate to elliptical leaves are distinctive for their double ribs, which don't reach to the tip.  Leaf cells are roundish to rectangular, with distinctive papillae, at least near the leaf tip. Spore capsules are symmetrical, somewhat swollen but narrowed below the expanded tip, and turned sideways by a bend in the upper stalk.

Callicostella pallida can readily be recognized by the unusual double ribs.
This species, sometimes filed under the older name, Schizomitrium pallidum, so far is known from Louisiana, Alabama and Florida.  In Florida, it is found from Alachua and Clay Counties southward.

From other members of the family Pilotrichaceae, including Cyclodictyon varians, found in north Florida, with an unverified report from Hillsborough County, Callicostella differs by its more rounded and papillose leaf tip.
The spore capsules are swollen but constricted below the larger tip, and
bent to the side by a hook near the top of the stalk.
The cells at the tip of the leaf are papillose, i.e. contain small, hard,
translucent bumps, seen here as tiny, yellowish bright spots.


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