n8 GEXERAL BIOLOGY 



There are but two main groups of organisms plants 

 and animals. If these are not always sharply distinguished 

 among the lower organisms, they are distinct enough among 

 the higher ones. Our study is therefore, of two series of 

 forms, which we shall illustrate in the fewest possible types 

 that will serve to show the more important features of 

 their structure and development. Matters of function 

 and of relation to environment will for the present be left 

 largely in abeyance, while attention is fixed on the form 

 and relations of the types in each series. 



I. THE PLANT SERIES. 



The briefest admissable classification of plants is the 

 familiar one that assembles algae and fungi into one group, 

 and makes of the remaining plants three groups that are 

 somewhat more homogeneous and consistent, as follows: 



1. Thallophytes ; algae and fungi. 



2. Bryophytes; liverworts and mosses. 



3. Pteridophytes ; ferns, etc. 



4. Spermatophytes ; the seed plants. 



We have already studied a few representative Thallo- 

 phytes ; we shall now briefly examine a few representatives 

 of each of the three other groups. 



Bryophytes: Liverworts and Mosses. 



This is a group of comparatively small plants, of very great 

 diversity in appearance. Those that live in the drier situa- 

 tions, and that are more familiar to us, are mainly mosses; 

 but liverworts are common also in their proper haunts ; in 

 the moist shaded places of deep woods; on wet rocks by 

 stream . 



Conocephalus. Fig. 69 is a good form with which to 

 begin our study of the group. The plant body is a broad 

 flat thallus, which spreads over and attaches itself closely 



