POLYTRICHACEAE 1 7 



GEORGIA Ehrh. 



G. pellucida (L.) Rabenh. (Tetraphis pellucida Hedw.) 

 Common in moist woods on humus, less frequently on rotten 

 wood than farther north. Autumn-spring. 



Family 4. POLYTRICHACEAE 



Plants usually of a large size, the simple or slightly branched 

 stems growing from a creeping underground stem (except 

 Pogonatam brevicaule and P. brachyphyllum) . Stems with a 

 central woody strand, which is the nearest approach to a vascu- 

 lar bundle in the non-vascular cryptogams Leaves usually 

 narrow, with the base sheathing or at least with the basal part 

 of the leaf hyaline with larger cells. The costa bears on its 

 upper surface, except at the hyaline base, longitudinal strips of 

 tissue {lamellae) one cell thick and attached to the upper surface 

 of the costa by one edge; the upper cell of the lamella is often of a 

 different shape from- the others, and seen in cross-section is of 

 great value in determining species. The upper leaf cells are 

 usually hexagonal. The plants are usually dioicous with the 

 antheridia borne in conspicuous terminal rosettes. Capsule on a 

 long smooth seta, large, cylindrical or prismatic, with 4-6 angles. 

 Calyptra cucullate, covered with a dense felt of hairs, or at least 

 roughened at apex with short spinose projections. Peristome of 

 32 or 64 teeth, short, without joints, triangular in cross-section. 

 Columella expanded at the top into a circular membrane, the epi- 

 phragm, which is attached to the tips of the teeth, and helps control 

 spore distribution. 



Key to the Genera 



1 — Capsules square or six-angled Polytrichum 



Capsules cylindric 2 



2 — Calyptra hairy; leaves not crisped when dry Pogonatum 



Calyptra not hairy; leaves crisped when dry Catharinea 



POLYTRICHUM Dill. The Hair-cap Mosses. 

 (Plate II, Fig. i.) 



The leaves are large, not bordered, with a sheathing mem- 

 branous base and very numerous straight lamellae occupying 



