— 253 — 



a group of cells here and there which is divided, sometimes also 

 a single cell only has been divided. Fig. 5 a shows a part of an 

 old thallus with divided and not divided cells. 



I have mentioned above that the young unicellular specimens 

 might perhaps have their origin from aplanospores. I think it very 



Fig. 6. Dictyosphœria favulosa (Ag.) Decsne. 



a- b. c- different stages of cell-division, in a the cell contents have been contracted to balls, in 

 b the young cells fill up nearly the lumen of the mother-cell, in e the young cells are quite dev- 

 eloped, the walls of the mother cells are seen over the young cells (10 : 1). d. wall of a cell torn 

 loose from the neighbour-cell showing arrangement of hapteræ (25:1). e. small part of d more 

 magnified; in the small cells chromatophores are seen; the oval rings upon them are the bases of 

 the hapteræ, in one place the ends of the hapters broken of from the neighbour-cell are seen 

 (100:1). /. hapters between two cells seen from above showing their alternating arrangement 



(150 : 1). 



likely namely, that the above-mentioned balls, formed by the cell 

 division, may occasionally become free and be able to grow. 



In the quite young small plants the thallus is massive (fig. 5 c) 

 but by cell-division the cell layer in the periphery will grow larger 



