110 STRUCTURAL BOTANY 



generation is the more important as regards vegetative 

 development, the sporophyte being always dependent 

 upon the oophyte for a great part of its nutrition, and 

 never becoming free. This Sub-kingdom is that of the 

 Bryophyta, or mosslike plants. It includes two great 

 Classes, the true Mosses and the Liver worts. The 

 Mosses, the general appearance of which is familiar to 

 everyone, have a vegetative growth much like that of 

 the higher plants, with well-formed stems and leaves, 

 but all these organs belong to the sexual generation, 

 and so are not directly comparable with the leaves 

 and stems of the higher plants, which belong to the 

 asexual stage. The Liverworts, perhaps less generally 

 known to those who are not botanists, sometimes have 

 distinct leaves and stems not unlike those of the true 

 Mosses, but many of them have a much simpler 

 organisation, the plant showing no distinction of leaf 

 and stem, but consisting of an undifferentiated body 

 performing the functions of both these organs, and called 

 a thallas. We will take one of these simpler Liverworts 

 for our first type of the Bryophyta, because its oophyte 

 generation is much like the prothallus of a Fern, a fact 

 which helps us at once to grasp the true homologies 

 between plants otherwise so different. 



A. THE LIVERWOBTS 



TYPE VII. PELLIA EPIPHYLLA 



1. THE THALLUS 



Pellia epipliylla is one of the commonest Liverworts, 

 growing in very various habitats, sometimes by the sides 



