40 



being much smaller, others reaching up to 700 — 800 « in dia- 

 meter. Between the cells intercellular openings often occur in 

 which the hapterse grow rather long. 



Since I wrote my paper above quoted I have found much 

 more material of this species in my collections and have by means 



of it been able to see that the 

 cell-division takes place by 

 segregative cell-division and 

 quite in the same manner as 

 in D. javulosa only with a few 

 differences. Also in this species 

 the whole protoplasts with 

 the numerous nuclei and chro- 

 matophores are divided into a 

 number of balls most often 

 3 — 5, but while in D. javiilosa 

 these during their growth are 

 arranged in the same plane 

 as all the other cells in the 

 thallus, here in D. van Bossese 

 they are arranged also above 

 each other in two or some- 

 times 3 layers according to 

 the size of the cells and by 

 this way of division the poly- 

 stromatic thallus is developed. 

 Another difference is also pre- 

 sent; while namely in D. favu- 

 losa the cell division most often 

 takes place in a group of cells 



_. ^, , . , . „ „ in D. van Bossese it is found 



Fig. 24. Dictmsph(eria van Bossece Borgs. , _ ,, ^^ ■ ■ i 



a, part of the thallus seen from above, here and there often m a smgle 

 the cell above has been divided in three cell or in some few together 

 cells, b, transverse section of a voung t.- oo j ^ « \ 



plant showing the massive thallus. In (compare tigs. 2o and 24 a). 

 the intervalls between the cells the My supposition that in this 

 haptera are seen (10:1). "^ . ^ i ,, , • i-i n 



species also Valonia-hke cell- 

 division should take place, 1 have not confirmed, having now 

 examined more material. 



Whilst, as mentioned above, I have not succeeded in finding 

 any trace of zoospore-formation in D. favulosa, I have been so 

 fortunate as to find a specimen of D. van Bossees, whose cells 

 were about to form zoospores (Fig. 25). 



