Desmidiacese 



371 



These have been observed in Spondylosjum nitens (Wallich) Arch. (Wallich, '60 ; 

 Turner, '93), Closterium Cornu Ehrenb. (Lagerheim, '86), Hyalotheca neglecta Racib. 

 (W. & G. S. W., '98), H. dissiliens (Sm.) Breb. (W. & G. S. W., '07) and Cosmarium 

 bioculatwm Breb. (Nieuwlaud, '09). 



Fig. 233. Zygospores aiid aplanospores of Desmids. A G, Hyalotheca dissiliens (Sin.) Breb.; 

 A, vegetative filament; B, end view of cell; G and D, zygospores, x 338 ; E G, aplano- 

 spores, x 468. H K, H. neglecta Eacib. ; H J, aplanospores (a) ; K, zygospore, x 430. 

 L, Micrasterias denticulata Breb., x 100. M, Euastrum oblongum (Grev. ) Ealfs, x 180. 

 N, Cosmarium bioculatum Breb., x 425. 0, Penium suboctangulare W. West, x 328. 

 P, Arthrodesmus octocornis Ehrenb., 425. Q, Staurastrum granulosum (Ehrenb.) Ealfs, x 468. 



Sexual reproduction of a low, and probably degenerate, type occurs by the 

 conjugation of two individual cells and the fusion of two large equal gametes 

 to form a zygospore. The conjugation is similar to that in the Zygnemacese 



242 



