382 



and PorcUa are most abundant. One species is semi-aquatic in 

 bogs. 



Schiffner* recognizes twenty-six genera. Strongly in contrast 

 with this arrangement is that of Spruce,t in which ten of the 

 genera recognized by Schiffner appear as sub-genera of Cephalo- 

 zia. Probably a more rational arrangement would be reached in 

 a mean between these two somewhat extreme views. 



The genera represented in temperate and boreal North Amer- 

 ica may be separated by the following artificial synopsis based on 

 forms lacking the sporophyte or perianth as species are often met 

 with in this condition :% 



Leaves succubous or rarely transverse ; plants small or minute (except in some species 

 of Odontoschisma). 



eaves deeply bidentate or bifid. 



Underleaves rarely present except on perianth-bearing branches. 



Cephalozia. 

 Underleaves well developed. 



Without root hairs ; underleaves like those of the stem. 



Hygrobiella. 

 With root-hairs ; underleaves undivided. Pleuroclada. 



Leaves rounded, entire or nearly so. Odontoschisma. 



Leaves incubous ; plants larger, often conspicuous (except in Lepidozia). 



Leaves rounded, entire or minutely twotoothed ; perianth wanting, the sporo- 

 phyte rising from a buried pouch. Kantia. 

 Leaves narrowed toward the end, usually 3-toothed. Bazzania. 

 Leaves palmately 3-4-cleft or divided. Lepidozia. 



* Hepaticae, in Engler-Prantl : Die natiirl. Pflanzenfam. 13: 94-103. 1893. 



\ On Cephalozia. 1882. 



\ The question so frequently asked by those who collect mosses is again answered 

 here : "Why is it that we find hepatics so rarely in fruit?" In the first place the 

 " fruit" {sporophyte) of the hepatic is less conspicuous than that of the true mosses 

 and the seta is often short. The first answer then is : " Because you overlook it." 

 In the second place there is a fundamental difference between the sporophyte of the 

 hepatic and that of mosses. In the mosses the capsule develops after the seta ; the 

 seta is, therefore, a somewhat permanent structure and the moss remains " in fruit" 

 for a considerable length of time. In the hepatic the capsule develops within the 

 calyptra (which in turn is surrounded by the perianth) until fully mature when the 

 seta develops, pushing through the calyptra ; the seta is, therefore, a temporary and 

 usually ephemeral structure, often withering away soon after the spores are scattered. 

 The perianth is a more permanent structure, and specific and even generic characters 

 are founded on it. Some stage of its development can usually be found in most 

 hepatics. Except in a few cases the characters of the sporophyte are unimportant 

 from a taxonomic stand])oint when generic and specific limits are considered, a condi- 

 tion of things widely different from that which obtains among the mosses. 



