EUTHALLEPHYTA— EUPH YCEA E 



191 



Fig. 33. Fresh Water Green 

 Slimes. Conjugatae. Left hand figure; 

 n — Zygnema. 1. Stellate chlorophyll 

 grain. 2. Zygospore. Right hand fig- 

 ure., s — Spirogyra chlorophyll in a 

 spiral band. 1, 2, 3 and 4, in different 

 stages of conjugation. 4. Zygospore. 



Fig. 33a. Botrydiaceae. Green 



Scum. Botrydium granulatum. 1. A 



single large zoosporangium. 2. Rhizoid 

 process. 



nucleated cells or, in some instances, only 1 or 2; chloroplasts occur on the mar- 

 gins with a single pyrenoid in each piece of the reticulum. The Siphoneae 

 contain the Vaucheria, found in damp ground, the long unsegmented threads of 

 which produce antheridia and oogonia, and the Botrydium granulatum found 

 on damp ground. 



VOLVOCACEAE 



Unicellular organisms or forming colonies, each cell with a single chroma- 

 tophore; forms gametospores and oospores. 



Pandorina, Bory 



The algae of this genus are collected together in spherical or subspherical 

 colonies known as caenobia. Each caenobium contains about 16 cells closely 

 packed within a gelatinous envelope; the cells are pyramidal in shape and reach 

 almost to the center of the spherical colony; each cell produces 2 cilia. 



Volvox, (L.) Ehrenb. 



Volvox consists also of globose colonies known as caenobia, each consisting 

 of a large number of small cells from 200 to 22,000, arranged in a single layer 

 within a gelatinous sheath; the caenobium is a hollow sphere, the cells being 

 connected by protoplasmic threads of varying stoutness; each cell has a distinct 

 chloroplast, 2 or more contractile vacuoles and a number of cilia ; reproduction 

 occurs through asexual methods or by fertilization; in fertilization, the sperm 



