Fig. 159 Cryptophyceae. A, Cryptomonas anomala, side view. 



B-D, Tetragonidium verrucatum, D, being the swarmer. / = furrow, 



n = nucleus, p =pyrenoid, s = starch. (After Fritsch.) 



PYRROPHYCOPHYTA 



Cryptophyceae 



Fig. 159 

 Very little is known about this group. They are mostly specialized 

 flagellates with two flagella but there are a few algal forms, al- 

 though none of them is filamentous. The morphological types are: 



(a) Naked motile unicells. 



(b) Colourless unicells. 



(c) Symbiotic unicells with cellulose walls, e.g. some of the Zoo- 

 xanthellae which are found associated with Coelenterata and 

 Porifera. 



{d) Palmelloid type, e.g. Phaeococcus, which is found on salt 

 marsh muds in England. 



{e) A single coccoid type, Tetragonidium. 



The number of chloroplasts varies, pyrenoids are present, and 

 there is one nucleus in each cell. Reproduction is by means of longi- 

 tudinal fission but some species also form thick-walled cysts. 



DiNOPHYCEAE 



Fig. 160 

 This group is predominantly planktonic, naked forms being most 

 abundant in the sea, whilst in fresh waters one commonly finds 



275 



