CHAPTER VII. 



BRANCH I. PROTOPHYTA. 



THE WATEE-SLIMES, OK SEXLESS PLANTS. 



216. The protophytes are the lowest and simplest 

 plants, and they are often so minute as to require the high- 

 est powers of the microscope for their study. For the 

 most part the cells are poorly developed; the protoplasm is 

 frequently destitute of granular contents ; and the nucleus 

 is wanting or poorly defined in many cases. 



217. The cells in all cases cohere little, if at all; and 

 even when they are united into loose masses each one re- 

 tains nearly as much independence as in the single-celled 

 forms. 



218. No sexuail organs are known. The common mode 

 of reproduction is by the fission of cells, although internal 

 cell-division occurs also. 



219. Most protophytes live in water and get their food 

 from the solutions it contains. Some are blue-green or 

 brown-green, and so are able to use carbon dioxide, while 

 others are destitute of a green color and are parasites or 

 saprophytes. 



220. This branch contains the single class ScHizo- 

 PHYCB^, the Fission Algas, of about 1000 species, separable 

 into two orders as follows : 



Plants strictly one-celled Order 1, CTSTiPHOKiE 



Plants few- to many-celled, forming threads. Order 3, Nematogenb^ 



135 



