CULTURE AND MORPHOLOGY 81 



(1949) on the green algae of the west coast of Sweden he re- 

 turned the family to the Ulvales, without comment. 



Yamada and Saito noted some interesting deviations in the 

 reproductive phase of two Japanese species of Monostroma. The 

 zygospore of M. angicavum Kjell. produces a comparatively large 

 number of zoospores (fig. i) and M. pulchrum Farl. lacks a sexual 

 phase. The plants obtained in nature produce quadriflagellate 

 zoospores, which form cysts. Following a resting period of about 

 eight months and a half, each cyst gives rise to a large number 

 of quadriflagellate zoospores which produce new plants. Quadri- 

 flagellate zoospores are thus formed at two stages in the life his- 

 tory of M. pulchrum Farl. 



In 1940, Moewus reported that subjecting the mature zygo- 

 spores of M. Wittrockii Born, to gametophyte extract caused the 

 zoospores, formed later in the cysts, to behave as gametes and in 

 some instances to produce two instead of the usual four flagella. 

 On the other hand, a similar treatment of gametes with zygote 

 extract did not cause them to lose their sexual power. 



Jorde (1933), working on the west coast of Norway, has 

 brought forth fairly conclusive evidence indicating that certain 

 species of the unicellular Codiolum (fig. 2), a genus of the family 

 Chlorococcaceae in the order Chlorococcales, represent the dif>- 

 loid asexual generation of species of the filamentous Urospora, 

 a member of the family Cladophoraceae in the Cladophorales. 

 These observations still require confirmation, but if they should 

 prove to be correct, we would have here an alternation of heter- 

 morphic generations, representing two kinds of green algae 

 which for a long time have been regarded as phylogeneticaily 

 very far apart. 



In this connection attention should be brought also to the 

 claim of Kornmann (1938) that Hcdicystis and Derbesia constitute 

 phases in the life history of one and the same alga. These genera 

 have been regarded as the type representatives of two distinct 

 families, Halicystidaceae and Derbesiaceae, of the order Sipho- 

 nales. 



Previous to the work of Kornmann, Hollenberg (1935) had 

 shown conclusively that the vesicular thallus of Halicystis (fig. 3) 



