BRITISH 



FRESH-WATER ALGK 



Algse are usually associated under five classes, which are 

 taken invariable order, according to the judgment of the author, 

 and may thus be enumerated : 



V 



I. CHLOROPHYLLOPHYCE^E, with the cell contents mostly of a 

 chlorophyll green. 



II. PHYCOCHROMOPHYCEJS, with the cell contents mostly of a 

 bluish green. 



III. MELANOPHYCE^:, with the cell contents olive, brownish, 

 or blackish. 



IV. RHODOPHYCE^E, with the cell contents rosy, purple, 

 crimson or violet. 



V. DIATOMOPHYCE.E, with an incombustible siliceous skeleton. 



Other arrangements have been proposed, but the above will answer for 

 all practical purposes. The third class are all marine, and the majority 

 of the fourth, so that, exclusive of Diatoms, which are a special study, 

 the fresh water Algae are mainly included in the first two classes. 



CLASS I. CHLOROPHYLLOPHYOE^J. 



Plants aquatic or aerial, one, or two, or many-celled, either 

 single or associated in families. Either branched or simple. 

 Cell wall not siliceous but combustible, sometimes composed of 

 successive layers, or strata, of a gelatinous substance. Cell 

 contents chlorophyllose, sometimes crimson, flesh-coloured or 

 reddish-brown, often with a central or lateral nucleus. Starchy 

 granules very rare. Vegetation by cell division. Fecundation 

 often sexual. Propagation either by oospores or zygospores or 

 gonidia, which are motionless or agile (zoogonidia). Rabh. 

 Alg. in. p. 1. 



* Exclusive of Desmidiese and Diatomaceae. 



B 



