33 



Referring to my earlier paper (Bot. Tidsskr. vol. 32, 1912, 

 p. 247) for the different interpretations in the botanical litera- 

 ture with regard to the development and systematic position 

 of the genus I confine myself here to giving a description of the 

 species found and their development. 



1. Dictyosphjeria favulosa (Ag.) Decsne. 



J. Decaisne, Classification des Algues, p. 32 (Ann. sc. nat., 2. Ser., 

 t. 16, 1842). Harvey, Ner. Bor.-Am., Ill, p. 50, tab. XLIV B ex parte. 

 J. Agardh, Till Algernes Systematik, VIII, p. 118, ex parte. Borgesen, 

 F., in Bot. Tidsskr., 32. Bd'., 1912, p. 250. 



Valonia favulosa Ag., Species Algarum, I, 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. 19), later on irregularly torn, forming expanded carti- 

 laginous membranes. 



In its first beginning the thallus consists of a single cell (Fig. 

 20 d) ; this can have a very variable shape, often very irregular, 

 being sometimes somewhat cylindric, sometimes oviform. The 

 basal part of the cell has a longer or shorter root-like pro- 

 longation (Fig. 20 c, e), upon the lowermost end and sides of which 

 we find a great number of small unicellular rhizoids which grow 

 out, one from each of the numerous small cells occurring here 

 very similar to those found in Valonia. Also higher up on the 

 cell we often find many of these small cells arranged as a rule in 

 rows (Fig. 20 d), some of them also more scattered. How far the 

 origin of these young plants are due to zoospores is difficult to 

 say, most probably they are not ; in the abundant material of 

 this species I have examined not a trace of zoospore-formation 

 has been found ^) and this has never been found by other investi- 

 gators. Much seems to suggest that these young individuals 

 are due to cells loosened from the thallus of other specimens. 

 This seems also to be indicated by the fact, that the wall of the 

 cells is often densely covered by Melobesiese and other epi- 

 phytes. Perhaps some of them also can have their origin from 

 aplanospores, about which more later on. 



As mentioned above the young plants are unicellular but a 

 few were found consisting of a few cells (see Fig. 20 e). Most 

 probably the 3 cells in this figure have been torn from an old 

 plant at once. 



^) compare the note, p. 37. 



