EUPHYCOPHYTA 



113 



whilst in transverse section the plastid has the appearance of a hub 

 with radiating spokes or else looks like a coarsely cogged wheel. 

 Cell division is pecuhar and takes place by one of two methods 

 producing either {a) connecting bands which appear as striae in the 



Fig. 64 Closterium. A, C. lanceolatum, chloroplast structure. B, 

 Closterium sp., structure in transverse section. C, C. lineatum, first 

 stage in conjugation. D, C. rostratum var. brevirostratum, zygospore 

 formation, second stage. E. C. calosporurrij mature zygospore. F-J. 

 C. ehrenbergii, stages in cell division. n= nucleus. (E, after Smith; 



rest after Fritsch.) 



older semi-cells or (b) girdle bands (cf. Fig. 65). In small-celled 

 species the process occupies about a day but a longer period is re- 

 quired with large-celled species. At conjugation, papillae from the 

 two cells meet or else the naked amoeboid gametes fuse immedi- 

 ately outside the cells, whilst in C. parvulum there is some evidence 



