90 BOTANY 



the door to knowledge of past continents that have 

 vanished with their floras. 



With the actual origin of plant life botanists would 

 gladly deal had they any data. That is hid in the en- 

 tirely impenetrable past however, and we return to the 

 study of the present flora as it is represented in the 

 simplest Thallophytic forms which still multitudinously 

 inhabit the earth. It is probable that there we see 

 the comparatively unchanged descendants from the 

 simple forms which were among those which early in- 

 habited the waters. Still, to-day there are some which 

 have such a mixture of the characters of both plants 

 and animals that it is almost impossible to say to which 

 group they belong. Here we see, as we noticed in the 

 cytological study of the most complex process, in the 

 highest plants and animals an extraordinary unity 

 between the two great branches of the tree of life. 



