•ORTHOTRICHACEAE 53 



ing in other situations where the trees stand somewhat apart. 

 They can be found abundantly on almost any fruit or shade 

 tree in the country. In the larger cities, for some reason, they 

 do not seem to thrive. They may frequently be found growing 

 with Ulota, from which the immersed or emergent capsule and 

 non-crisped leaves distinguish them at once. The calyptras are 

 less densely hairy than those of Ulota. Two species have a 

 calyptra without hairs. The leaves have revolute margins, 

 except in 0. obtusifolinm. Driimmondia has the general ap- 

 pearance of an Orthotrichiim with an exserted capsule, but the 

 calyptra is cucullate and without hairs and the capsule is not 

 wrinkled when dry. 



Sterile specimens are often indeterminable. The stomata 

 furnish an excellent and definite microscopic character and are 

 easily observed by separating a capsule into two or more divi- 

 sions with the dissecting needles and mounting outside up; 

 the stomata are nearer the middle of the capsule than in many 

 mosses and are therefore, easier of observation. The condition 

 of the material is of the utmost importance. The capsule 

 must be thoroughly soaked in hot water for a long time to be 

 fully expanded, and the dry capsule must be thoroughly dry to 

 be characteristic. The capsules of all species shrink progres- 

 sively with increasing age, and many varieties had their origin 

 in this fact. The plants should be moistened to determine 

 whether the capsules are immersed, emergent, or exserted. 

 The peristomes are often quite brittle and are apt to be broken, 

 especially the segments. For identifying species, perfect calyp- 

 tras are of the greatest value and importance. 



Key 

 I — Rock-inhabiting species; peristome single, teeth 16, erect or erect- 

 spreading on dry capsules, stomata immersed 2 



Tree-inhabiting species; peristome double, teeth usually united 



into 8 pairs, recurved or reflexed when dry 4 



2 — Capsule fully exserted, 16-striate anomahim 



Capsule immersed or emergent, 8-striate 3 



3 — Capsule ovate-cylindric, urn half emergent when dry Porteri 



Capsule much shorter, ovate-globose, leaves nearly reaching mouth 



of urn when dry Lescurii 



4 — Stomata superficial {i. e., with both guard-cells on the surface) 5 



Stomata immersed 6 



