HYPNACEAE 241 



Plagiothecium denticulatum (L.) Bryol. Eur. and 

 Plagiothecium sylvaticum (Huds.) Bry^ol. Eur. very 

 closely resemble each other. P, denticulatum is proba- 

 bly more frequently collected. The plants arc much 

 larger than most of the species of Isopicrygium, the 

 preceding genus. The leaves are usually glossy. P. 

 sylvaticum has been described as less glossy than P. 

 denticulatum y but this characteristic alone is not sufli- 

 cient for field identification. The moss that most 

 closely resembles these two Plagiotheciums is Rhyn- 

 chostegium serrulatum (p. 256). The leaves of that 

 species are less glossy, but the only satisfactory field- 

 mark is the beak of the operculum. In Rhynchostegimn 

 it is noticeably long, slender, and curved, while in 

 Plagiothecium it is shorter, and often the operculum is 

 only cone-shaped. BrachytheciumStarkei(p. 248) has a 

 flattened appearance, but this is not so conspicuous as 

 in Plagiothecium, as the leaves of the former are smaller 

 and narrower. Fruited specimens can be easily dis- 

 tinguished, as the capsule of Brachythecium is short 

 and stout and that of Plagiothecium is long and slender. 



Plants small, growing in close mats on the ground, on 

 rocks (but not on limestone), and on decaying logs in moist 

 woods; rather dark green or yellowish-green; common in 

 swamps; fruit frequent, often abundant. 



Stems prostrate, irregularly branched; branches short, 

 about % of an inch long; erect, crowded. 



