85 



capsule is unsynunctric, inclined, yellow brown at maturity. I lie leaves 

 are serrate, acuminate, yellow green, linear lanceolate. The costa ia 

 thick and reddish. Mature in summer and spring. 



POLYTRICHUM. 



The Polytrichunis are all large mosses and are among our most common 

 forms. They grow from underground stems, and bear lamellae on the 

 back of the leaf. Capsules are borne on long seta and are angled. Male 

 plants are easily distinguished by the arrangement of the leaves at the 

 summit of the plant in rosettes. The calyptra is densely hairy. f)ur two 

 most common forms are described below. 

 P. commune. 



The leaves are costate, serrate, open recurved, long sheathing. Capsule 

 is sharply angled, cubical with short beak. Operculum short, seta long. 

 Plants large, very loosely cespitose, in woods or open fields. Mature in 

 spring. 

 P. ohioense. 



Closely resembles the preceding. The capsule, however, is longer than 

 broad, with a long beak. The beak is tapering. It grows in deeper woods 

 and in more moist situations. 



POTTIA. 



P. iruncatula. 



Capsule is urn shaped. Leaves are costate, entire, acute and mucronate. 

 They are ovate and oblong. The costa is excurrent. Seta short and 

 slender. Plants grow in open ground, form loose mats, small, dull green 

 in color. Potlia resembles Physcomilrium from which it differs in the 

 excurrent costa and in time of maturity. Pottia matures in the autumn. 

 Ptychomitrium. 

 P. incurvum. 



Calyptra is plicate. Capsule oval, erect. Leaves crispate when dry, 

 erect, incurved when wet. The leaves are linear lanceolate, entire, with a 

 costa which reaches to just below the apex. The apex is acute. The 

 plants grow on rock, forming dark green, dense cushions. Plants mature 

 in winter or in early spring. 

 Rhacomitrium. 

 R. aciculare. 



A form difficult to distinguish without the aid of a microscope which 

 will reveal the sinuose walls. This species closely resembles Grimmia, 

 but the plant is much larger, and is found in subalpine regions on wet 

 rocks. The leaves are costate, not hyaline tipped. The margin is 

 recurved, it is entire, with a few low teeth at the apex, which is round- 

 obtuse. The leaf is ovate-oblong in shape. The calyptra is mitrate, 

 long-beaked, smooth. The capsule is exserted. The seta is erect and 

 straight. Mature in the spring. 

 Rhodobryum. 

 R. roseuvi. 



The capsule is fairly large, clustered, pendent, smooth. Seta long, 

 operculum conical, apiculate. The leaves are costate, serrate, obtuse. 



