THALLOPHYTA: ALGAE 93 



carp and carpospores. The gametophyte generation begins with the 

 tetraspore. 



Summary. In the Rhodophyceae both chlorophyll, with its associated 

 carotinoids, and a red pigment (phycoerythrin) are present in the plastids. 

 With only a few possible exceptions, all members are multicellular, the 

 thallus being most commonly filamentous but often plate-like. The cells 

 contain a definite nucleus (sometimes more than one), one or more 

 plastids, and a cell wall that is often gelatinous. Reserve food is stored 

 chiefly as "fioridean starch." Reproduction occurs by means of aplano- 

 spores and heterogametes. The female organ is a carpogonium. Carpo- 

 spores arise from the zygote, either directly (in the Bangiales) or indi- 

 rectly (in the other Rhodophyceae). Except in the Bangiales and 

 Nemalionales, both carpospores and tetraspores are produced, the latter 

 by a sporophyte. All reproductive cells are nonciliated. No resting 

 cells are formed. A distinct alternation of generations is a feature of all 

 red algae except the Bangiales and Nemalionales. The gametophyte and 

 sporophyte are similar vegetatively. 



COMPARISON OF THE CLASSES OF ALGAE 



The most important distinguishing characters of the ten classes of 

 algae are as follows: 



Cyanophyceae. Cells containing, in addition to chlorophyll and 

 carotinoids, a blue pigment (phycocyanin) and frequently a red pigment 

 (phycoerythrin) also. Pigments not confined to definite plastids. 

 Reserve food stored as glycogen. Plant body unicellular, generally 

 colonial. Cells without a well-organized nucleus. Cell walls usually 

 forming abundant mucilage. Reproduction by fission, never by zoo- 

 spores or gametes No ciliated cells. 



Euglenophyceae. Cells with green plastids containing an excess of 

 chlorophyll over the carotinoids; frequently colorless. Reserve food 

 stored as paramylon. Unicellular and usually solitary; sometimes 

 colonial. Cell walls almost always absent. Free-swimming or, when 

 colonial, attached. Reproduction by fission, rarely by isogametes (?). 

 Motile cells with one or two ciha attached anteriorly, equal or unequal. 



Chrysophyceae. Cells with golden brown plastids containing chloro- 

 phyll and an excess of carotinoids; sometimes colorless. Food stored as 

 oil or leucosin. Unicellular and often colonial, rarely multicellular. 

 Cell walls almost always absent. Free-swimming or sometimes attached. 

 Reproduction by fission, and sometimes by zoospores, rarely by isoga- 

 metes (?). Motile cells with one or two cilia attached anteriorly, equal 

 or unequal. 



Dinophyceae. Cells with yellow-brown plastids containing chloro- 

 phyll and an excess of carotinoids, or colorless, storing food as starch or 



