FRESH-WATER ALG/E OP THE UNITED STATES. 



Class PIIYCOCHROMOPIIYCEJE. 



PlcmtcB uni- vel multicellulares, in aqua vigentes vel extra aquam in 

 muco matricali nidulantes, plerumque familias per cellularum gencrationes 

 successivas ortas formantes. 



Cytioderma non siliceum, combnstibile. 



Q/tioplas7na phycochromate coloratnm, nucleo dcstitutum, granulis 

 amylaceis plerumque nullis. 



Propaijatio divisione vegetativa, gonidiis immobilibus vel sporis tran- 

 quillis. 



Unicellular or mvlticelMar plants living in water, or incased in a mater- 

 nal jelly out of it, mostly in families formed from successive generations 

 of cells. 



Cytioderm not siliceous, combustible. 



Cytioplasm an endochrome, brown, olivaceous, fuscous, &c., destitute 

 of nucleus, mostly witliout starch granules. 



Propagation by vegetative division, by immovable gonidia or tranquil 

 spores. 



The phycochroms are plants at the very bottom of the scale, distinguished by 

 the simplicity of their structure and the color of their protoplasm, which, instead 

 of being of the beautiful green that marks chlorophyll, is fuscous, or yellowish, 

 bluish, brownish, or sometimes particolored, and rarely greenish, but of a shade 

 very distinct from the chlorophyll green, more lurid, bluish or yellowish, or oliva- 

 ceous in its hue. The nucleus appears to be always wanting. The cell wall is 

 oftentimes distinct and sharply defined, but in many instances it is not so, the 

 walls of different cells being fused together into a common jelly in which they are 

 imbedded. In a large suborder the wall is replaced by a sheath, which in some 

 genera surrounds cells with distinct walls, in others, cells without distinct walls, 

 and in still others, a long cylindrical mass of endochrome, which may be looked 

 \ipon as a single cell. 



Many of the phycochroms are unicellular plants in the strictest sense of the word, 

 but more often the cells are conjoined, so as to form little families, each cell of 

 which is in a sense a distinct individual capable of separate life, yet the whole 

 bound together into a composite individual, llarely tlie pliycochrom is a multi- 



2 January, 1872. ( 9 ) 



