CULTURE AND MORPHOLOGY 83 



is gametophytic in nature. Tlie plants are dioecious and form 

 terminally biflagellate anisogametes. The zygotes form Vau- 

 cheria-\\kt filaments which produce erect branches of limited 

 growth and rhizomes which penetrate encrusting corallines, the 

 customary hosts. HoUenberg (I.e.) believes that the rhizomes 

 give rise to Hcdicystis plants on the surface of the host. 



Starting with the stephanokont zoospores (fig. 4c) of the 

 siphonous Derbesia (fig. 4a), Kornmann found that these cells 

 gave rise to non-septate filaments which in the course of time pro- 

 duced vescicles which in every respect resembled plants of Hali- 

 cystis. These vesicles became fertile in the same way as Halicystis 

 does and formed zooids which resembled the gametes of this 

 genus. Although no conjugations were observed, Kornmann be- 

 lieves that the zooids actually were gametes, because new plants 

 developed only in those cultures which contained both large and 

 small zooids. The "zygotes" produced Vaucheria-Xikc filaments 

 which were believed to be early stages in the development of 

 Derbesia plants. 



In view of the differing conclusions of HoUenberg in respect 

 to the life history of Halicystis, it is evident that the work of 

 Kornmann is in urgent need of repetition. In the opinion of the 

 present author the great difference in the type of flagellation in 

 the motile cells of Halicystis and Derbesia would suggest no 

 close connection between these genera. In fact, Derbesia is almost 

 as much of a misfit in the Siphonales as was Vaucheria before 

 Eubank (1949) removed it to the Xanthophyceae, where it at 

 one time had been placed.*^ 



Prominent among the more outstanding work of recent times 

 on marine Chlorophyta, is that of Hammerling (1931, 1932, 1934, 

 1943, 1944, 1946, and other papers) and his associates (Schulze, 

 1939; Beth, 1943; Maschlanka, 1946) upon Acetabularia and 

 other Dasycladales. A significant feature of this work is that it 



^ In an article which appeared since this paper was written, Feldmann 

 (Compt. Rend. Acad. Sci., Paris, 250 (3): 322-323. 1950) upholds the 

 contention of Kornmann that Derbesia and Halicystis are phases in the 

 life history of one and the same genus. 



