134 BOTANY. 



phyll, those of but five or six families being destitute of it. 

 The green forms are all aquatic, and inhabit either fresh or 

 salt waters. Those which have no chlorophyll are partly 

 saprophytes, living upon dead organic matter, while others 

 are parasitic, living upon and at the expense of living 

 plants and animals : they are doubtless to be regarded as 

 modified forms of some of the types of the chlorophyll- 

 bearing portion of the group. 



233. There are two classes of phycophytes, distinguished 



as follows : 



Chlorophyll-green one-celled or filamentous plants, rarely composed 



of a plate of cells, Class 2, CHLOROPHYCBiE 



Olive-green filamentous or massive plants, the latter with rhizoids, 



Class 3, Ph^ophyce^ 



Class 2. Chlosophyce.e. The Green- Alg^. 



234. These are typically green plants, containing ordi- 

 nary chlorophyll in their chloroplasts. In the simpler 

 cases they are one-celled, but typically they are composed 

 of simple or branched filaments, while in a few cases they 

 consist of a plate of cells. They are usually small or even 

 microscopic plants, rarely exceeding a few centimetres in 

 extent. For the most part they inhabit fresh waters, and 

 as a consequence they are commonly called the Fresh-water 

 Algse. The parasites and saprophytes of the group are 

 chlorophyll-less, and usually much degenerated. 



235. This class contains about 7000 species, distributed 

 among four orders, as follows : 



Plant unicellular, gametes mostly equal and motile, 



Order 3, Pkotococcoidb^ 

 Plant unicellular, or an unbranched cellular filament, gametes equal, 



not motile Order 4, Conjugate 



Plant tuhular, branched, gametes equal and motile, or unequal, 



Order 5, Siphoned 

 Plant a cellular filament, gametes equal and motile, or unequal. 



Order 6, ConfervoidBjE 



