88 



Chlorophycece 



than their own diameter, and they pass through many different 

 shapes in accommodating themselves to this small aperture. Usually 

 all the cells of a single cluster of branches produce zoogonidia 

 simultaneously, the entire performance occu- 

 pying only a few minutes. Resting akinetes 

 (hypnospores) are frequently produced from 

 the cells of the branches. 



There are two species, D. plumosa (Vauch.) Ag. 

 and D. glomerata (Vauch.) Ag. (fig. 29), widely dis- 

 tributed in the British Islands. They prefer clear 

 water and occur both in the still water of bogs and 

 amongst stones in streams. When growing in 

 streams they are usually found in quiet pools, 

 stretching in long, pale-green, gelatinous strands 

 (up to 20 cms.) from stone to stone. The lateral 

 branches of D. glomerata are fewer and much 

 shorter than those of D. plumosa, the cells are 

 proportionate^ a little longer, and the hairs are 

 also usually longer. The diameter of the primary 

 filaments is 40 50 p. and that of the cells of the 

 branches 5 10 p. Species of this genus are amongst 

 the prettiest of all freshwater Algae. 



Genus Pseudochaete West & G. S. West, 

 1902. The thallus consists of two portions, 

 a creeping portion and an erect portion. The 

 creeping part consists of cylindrical or barrel- 

 shaped cells, about 1^ 2^ times longer than 

 their diameter, each containing a parietal 

 chloroplast with one pyrenoid. The erect 

 branches arise at right angles to the creeping 

 portion; they are narrower and attenuated 

 to fine points, each one consisting of from 

 five to eight distinct cells. These cells are 

 from 8 to 18 times longer than their 



diameter and each contains an elongated 

 Fig. 30. Pseudochate .,, -. 



gradlis West & G. S. chloroplast, usually without a pyrenoid. 



West, from near Coates, Sometimes the terminal cells of the branches, 

 Gloucestershire ( x 520). , , . 



or even the two terminal cells, contain no 



protoplasmic contents and therefore no chloroplast. 



P. gradlis West & G. S. West (fig. 30) occurs as an epiphyte on 

 aquatic plants. The diameter of the cells of the creeping filaments is 57 



