THE GREEN ALG^ 107 



much in common, and on the whole, Botrydium seems most 

 happily placed for the present among the Heterokontae, although 

 occupying rather an isolated position in this group. 



In conclusion it may be mentioned that Scherffel (58) assumes 

 a relationship between the Cryptomonadineas and the Chloro- 

 monadinea? by way of a peculiar representative of the latter, 

 the genus Vacuolaria (Senn 6^^). This is a motile unicellular 

 form having two cilia of equal length, one of which, however, 

 points forwards and the other backwards (possibly a preliminary 

 to unequal development) ; these cilia arise from a depression 

 at the front end in the same way as do those of the Crypto- 

 monadineae (see the first part of this article, fig. i, s, p. 629). 

 The symmetry of the body in Vacuolaria, moreover, appears 

 to be dorsiventral, like that in the Cryptomonadineae. The 

 numerous chloroplasts of Vacuolana, on the other hand, agree 

 more with the characters of the Chloromonadineae. This can- 

 not, however, be regarded as establishing a very close relation- 

 ship, and we shall require to know a good deal more about 

 these two Flagellate groups before such an assumption can be 

 ratified. There is every reason to assume, however, that both 

 Cryptomonadineae and Chloromonadineae originated from a 

 common group of colourless Flagellates like those represented 

 by Senn's Protomastigineae (Senn 6^,) at the present day, but 

 such an origin probably lies rather far back in the Flagellate 

 series. We have thus traced the phylogeny of the green Algae, 

 as far as our present knowledge admits, along the numerous 

 lines of evolution originating from the Flagellate ancestry, which 

 formed the basis for the whole series of forms. 



Bibliography ^ 



1. Artari, Zur Entwickelungsgeschichte des Wassernetzes, Hydrodiclyon 



ittrkulatuni^ Roth., Bull. Soc. imp. d. Naturalistes de iMoscou, 1890, No. 2. 



2. , Untersuchungen iiber Entwickelung und Systematik einiger Proto- 



coccoideen, Bull. Soc. imp. d. Naturalistes de Moscou., 1892, No. 2. 



3. ASKENASY, ijber die Entwickelung von Pediastruj/t, Ber. deutsch. Bot. Ges. 



vi. 1888, p. 127. 



4. Berthold, Untersuchungen iiber die Verzweigung einiger Siissvvasseralgen, 



Nova Acta Acad. Leop.-Carol. xl. 1878. 



' In view of the very extensive ground covered by this article, only a very 

 limited number of literature-references could be included. In most cases the 

 inclusion of the most recent or most fundamental contribution on a certain topic 

 has been aimed at. 



