348 ON LYELLIA, LEPTOSTOMUM, 



579] By these lines also S. squarrosum is readily distin- 

 guished from Octoblepharum, in which the apparent number 

 of teeth is the same : for in Octoblepharum each tooth has 

 only a single pellucid line ; and hence its affinity to certain 

 species at present referable to Weissia, with a nearly similar 

 habit and sixteen distinct teeth, whose axis is not perceptibly 

 pellucid. 



Weissia splachnoides differs from the other Splachnea in 

 having sixteen equidistant teeth ; but as these teeth, accord- 

 ing to the indication of the pellucid axis, are double, the 

 arrangement may be compared with that of Tayloria and 

 Systylium, in which the separation into thirty-two is com- 

 plete, and the sixteen pairs equidistant. It agrees, however, 

 also in this respect with Grimmia and with several species 

 of Weissia : bnt in other important characters, as well as 

 in habit, it is evidently related to Splachnum, and offers 

 perhaps one of the best examples of the importance of the 

 male flowers in distinguishing natural genera. 



Even Tetraphis pellucida may be cited in proof of the 

 same prevailing number in the peristomium ; each of its 

 four teeth, when highly magnified, appearing to have seven 

 longitudinal strias, which, according to this test, would make 

 the real number thirty-two ; a structure contributing to fix 

 the place of Tetraphis in the natural series between Splach- 

 num and Orthotrichum. 



580] Better evidence on the same subject is afforded by 

 Trichostomum , Didymodon, and Leucodon,m all of which the 

 thirty-two teeth are distinct, though approximated in pairs ; 

 by the sixteen bifid teeth of Dicranum and Fissidens ; and 

 by the like number of teeth with a perforated axis in Tre- 

 matodon, Weissia nuda, Didymodon latifolium, and several 

 species of Grimmia. 



mosses differ materially even in this part of their structure ; and as other 

 differences, of at least equal importance, also exist, both in the peristomium 

 and male flowers, Octoblepharum serratum, whose habit is nearly that of Splach- 

 num, may be distinguished both from that genus and from Octoblepharum^ the 

 following characters. 



Okthodon. 



Fl. Fem. terminalis. 



Peristomium simplex, octodentatum, dente singulo striis tribus iongitudinali- 

 bus instructo (ideoque e quatuor coalitis composite). 



Calyptra mitriformis (4-fida, pilosa). 



FL Mas. terminalis, discoidcus. 



