DIVISION CHRYSOPHYTA 



This group, as now recognized, is large and includes an enormous 

 variety of plant forms which have, however, several fundamental 

 characteristics in common. First, their pigmentation is yellowish- 

 green or brown with carotinoids predominating. Second, the food 

 reserve is oil or leucosin rather than starch, and third, there is a 

 prevalent duplex character in structure of the wall, which in many 

 genera is composed of 2 spliced sections. The juncture of the two 

 halves may be along the longitudinal walls, or in the short diameter 

 of the cell. 



It is noteworthy that the division includes forms which present a 

 morphological evolutionary series comparable to that noted in the 

 Chlorophyta. There are unicellular non-motile and flagellated forms, 

 and in addition a rhizopodal type of cell which has no counterpart 

 in the Chlorophyta. There are simple, indefinite or definitely formed 

 colonies, simple or branched multicellular filaments, and siphona- 

 ceous thalli. 



Reproduction varies greatly according to respective classes and 

 families. Besides vegetative multiplication by cell division and 

 fragmentation, there are other non-sexual methods which involve 

 aplanospores, zoospores, or special modifications of these. It is inter- 

 esting that heterogamy has not been developed in this di\'ision, only 

 isogametes being known and these for a limited number of genera. 



Key to the Classes 



1. Chromatophores vellow-green, or if green not 



responding to iodine test for starch xanthophyceae 



1. Chromatophores brown or golden brown; oil bodies and 



leucosin granules usually conspicuous 2 



2. Cells capsule-like, the wall definitely 2-valved; silicious 

 and usually etched with punctae or striations; organs of 



locomotion absent; not forming cysts bacillariophyceae 



(Diatoms— See Appendix p. 939) 

 2. Cells not capsule-like, the wall not 2-valved; pectic, with silicious 

 impregnations not distinct; flagellated or rhizopodal cells common; 

 forming endogenous cvsts with silicified walls chrysophyceae 



CLASS XANTHOPHYCEAE 



The most noticeable characteristic of this class is the predominance 

 of yellow pigments in the chromatophores, causing the cells to 

 appear pale green, in contrast to the Chlorophyta. In many forms 

 the cell content possesses a metallic lustre as a result of leucosin 

 accumulations which, together with oil, constitute the chief food 

 reserves. 



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