ii6 



XANTHOPHYCEAE 



cytoplasm where it is associated with numerous discoid chloro- 

 plasts. A new membrane is formed internally and then the old one 

 ruptures, but as the latter may still persist outside one can often see 

 what appears to be a multi-layered sheath. Reproduction can take 

 place by means of zoosporic swarmers but these may be replaced 

 by aplanospores, whilst resting cysts are also recorded. Although 

 most abundant in the warmer oceans, especially during the winter 

 months, its life history is as yet only imperfectly known. 



A X B 



Fig. 80. Fig. 81. 



Fig. 80. Halosphaera viridis. A, mature cell. B, young cell in optical section. 

 C, mature cell with aplanospores. D, swarmer. (A-C, after Fritsch; D, after 

 Dangeard.) 



Fig. 81. Characiopsis saccata. A, plant. B, probable swarmer formation. 

 (After Fritsch.) 



Chlorotheciaceae : Characiopsis (like Characium). Fig. 81. 



The very name of this genus indicates that it is an analogue to the 

 genus of similar name in the Chlorophyceae. The plants, which are 

 epiphytic, solitary or gregarious, vary much in shape, even in 

 pure culture, and they develop from a short stalk with a basal 

 mucilaginous cushion. The wall, composed of cellulose and pectins, 

 is in two unequal portions, the smaller upper part forming a lid 

 which is detached at swarmer formation whilst in one species the 

 lower part bears internal processes. Although the young cells are 

 uninucleate and contain one or more chloroplasts the adult cells 

 are multinucleate containing eight to sixty-four nuclei. Reproduc- 

 tion is either by means of zoospores (eight to sixty-four per cell) or 

 else by means of thick-walled aplanospores, which in one species 



