ORTHOTRICHACEAE 121 



except in U. amcricana, which grows on rocks and has 

 the leaves folded straight when dry, and cannot be 

 easily distinguished from Orthotrichum anomalum. For 

 comparison with that species see p. 118. U. Ludwigii 

 and U. ulophylla are the common species found on 

 trees. They are distinguished from each other by cer- 

 tain characteristics of the capsules that are not always 

 clearly defined. Typically the capsule of U. Ludwigii 

 is pear-shaped, with a very narrow mouth, while in U. 

 ulophylla the capsule is contracted below a much 

 wider mouth, then gradually narrowed toward the 

 base. Ulota phyllaniha, which also grows on trees, 

 more rarely on rocks, is a larger, more robust species 

 than the preceding, is less frequent, and very rarely 

 fruits. 



