52 ORTHOTRICHACEAE 



immersed ; in Ulota the seta is long enough to exsert the capsule 

 entirely beyond the perichaetial leaves. 



The remarks in the discussion of Orthotrichum on the condi- 

 tion of capsules suitable for study apply equally to Ulota. 



Key 



i — Growing on rocks; leaves not crisped Americana 



Growing on trees; leaves crisped when dry 2 



2 — Capsule abruptly narrowed to the small mouth, smooth except near 



the mouth Ludivigii 



Capsules wide mouthed, distinctly plicate crispa and var. crispula 



U. Americana (Beauv.) Lindb. Common; reported as oc- 

 casionally occurring on trees. Summer. 



U. Ludwigii Brid. On trees, Closter, N. J., Austin, Bx! 

 Autumn. 



U. crispa Brid. Frequent in outlying districts. Spring- 

 summer. 



Var. crispula (Bruch.) Hamm. "On trees, particularly 

 Betnla lutea, rather scarce," Muse. App. 159; Closter, N. J., 

 Austin, Bx!; Jamaica L. Id., Brainerd (H. S.) 



ORTHOTRICHUM Hedw. (Plate IV.) 



Plants comparatively short-stemmed, in close rounded cush- 

 ions, sometimes looser, on trees everywhere, and more rarely 

 on rocks. Leaves hygroscopic, imbricated when dry and not 

 greatly curled or twisted, which character separates the genus 

 from Ulota except U. Americana. Upper leaf cells usually 

 papillose, thick-walled, the lower thinner-walled and quadrate 

 to rectangular. Calyptra sparsely hairy or naked. Base of 

 seta enclosed in a minute cup-like sheath, the ochrea. Capsule 

 immersed or emergent, rarely exserted; usually with 8 regular 

 folds, or plicae, when dry, but sometimes smooth or with 16 

 plicae. Peristome usually double, with 16 broadly lanceolate 

 teeth, which are usually united in pairs. Inner peristome of 8- 

 16 narrow segments, often called cilia. The paired (bigemrni- 

 nate) teeth and degenerate inner peristome illustrate well the 

 degeneracy of peristomes on erect capsules. 



The Orthotrichums are most frequent on trees about houses, 

 and in orchards and village streets, although they are not lack- 



