CLASSIFICATION OF THALLOPHYTES. 335 



ARRANGEMENT OF THE CLASSES OF THE CARPOSPORE.E. 



VI. THE CLASSIFICATION OF THALLOPHYTES. 



(1.) The classification of the Thallophytes, outlined in the preceding 

 pages, is essentially that given by Sachs in the fourth edition of his 

 " Lehrbuch." Sachs, however, considered the Protophyta, Zygosporeae, 

 Oosporeae, and Carposporese to be Classes, whereas in this book they are 

 raised to Divisions, co-ordinate with Bryophyta, Pteridophyta, and Pha- 

 nerogamia. It is evident, even from the hasty examination sketched in 

 the preceding pages, that there are three well-marked kinds of repro- 

 ductive apparatus in the Thallophytes, which are, to a considerable 

 degree, distinct. There are, of course, here and there cases in which 

 one kind merges into another, but this is no more than is to be observed 

 in everything else throughout both the vegetable and animal king- 

 doms. After making all due allowance for the doubtful cases, the fact 

 yet remains that there are three kinds of reproductive apparatus in the 

 Thallophytes, which are as readily distinguishable as are those of the 

 Cormophyte Divisions, Bryophyta, Pteridophyta, and Phanerogamia. 



(2.) Of the differentiation of tissues we know less ; but enough is 

 known to warrant the statement that, as in the Divisions of theCormo- 

 phytes, there is a progressive increase in complexity as we pass from 



