— 250 — 



by haptera, not by incrustation". The development of the plant 

 is described in this way : "In younger solid plants the cells are of 

 equal size. Soon those in the center enlarge and through the 

 growth of outer cells become torn and disorganized. The hollow 

 thus formed enlarges by the same process. The thallus lacks 

 cohesion, gained by interlacing branches in Struvea, and is bound 

 together by a membrane; this now splits in all directions causing 

 the thallus to rupture". Miss Crosby gives a detailed description 

 of the needles in the interior of the cells, of the hapters etc. 



Her description seems essentially to 

 be based upon D. Versluysi but she 

 seems also to have had specimens of 

 D. favulosa. 



Finally I may yet add that in "Icô- 

 nes of Japanese Algæ", vol. 1 (1907—9), 

 pi. XL, fig. 13— 24, Okamura gives 

 some illustrations of our plant. Judging 

 from his figures it seems to be evident 

 that he has had in hand the true Diet, 

 favulosa. 



Fig. 4. A young plant of 

 Dictyosphœria favulosa 

 (Ag.) Decsne. 



Its thallus is hollow and consists of 

 a single layer of cells. (About 6:1). 



After this survey of the different 

 interpretations in the botanical literature 

 with regard to the development of the thallus of this genus I shall 

 now give a description of what I have found in my material. 



Dictyosphæria favulosa (Ag.) Decsne. 



J. Decaisne, Classification des Algues, p. 32 (Ann. sc. nat., 2. Sér., t. 16, 

 1842). Harvey, Ner. BoivAm., Ill, p. 50, t. XLIV B ex parte. J. A g ard h , 

 Till Algernes Systematik, VIII, p. 118, ex parte. 



Valonia favulosa Ag., Species Algarum, 1, p. 432. 



Of this species I have collected an abundant material and it 

 is especially upon this that I have based my investigation of 

 the genus. 



As already pointed out by Harvey the young specimens are 

 globose (Fig. 4), later on irregularly torn, forming expanded carti- 

 laginous membranes. 



In its first beginning the thallus consists of a single cell (fig. 5 d) ; 

 this can have a very variable shape ; often very irregular, being 

 sometimes somewhat cylindric, sometimes oviform.' The basal part 



