?80 G. F. PAPENFUSS 



morpha. He has found that some of the species, and races of 

 others, lack a sexual generation and reproduce by asexual spores 

 only. In some instances, these are biflagellate and resemble 

 gametes, as in E. biflagellata Blid. (Eliding, 1944), and in others, 

 such as E. procera Ahln. (Eliding, 1933), they are quadriflagel- 

 late. Bhding (1938) has also shown that in its early development 

 £,, minima Nag. differs from other species in the possession of 

 an extensive prostrate system; and on the basis of this character 

 Kylin (1947) later removed this species to a new^ genus, Blidingia. 



Although many of the species of Enteromorpha, particularly 

 ;as represented in herbarium specimens, probably will continue to 

 defy precise identification, the cultural work of Eliding clearly 

 shows that from the point of view of life cycle and ontogeny, 

 marked differences exist between a number of the species. 



Monostroma is another genus of the Ulvales which has been 

 the subject of morphological study in recent times, with extreme- 

 ly interesting results. As early as 1878, this genus was studied 

 in culture by Reinke (1878a) who found that the plants obtained 

 from the sea were sexual in nature. The zygotes became resting 

 zygospores, the content of which in certain instances was divided 

 into cells after a period of 7 to 8 weeks. Reinke thought that this 

 was an early stage in the development of a Monostroma thallus. 



Kunieda (1934) was the first to show that after a rest period 

 ■of about five months, the thick-walled zygospores each formed 

 about 32 quadriflagellate zoospores. These observations have been 

 confirmed by Yamada and Saito (1938) and by Moewus (1938), 

 the latter having shown also by cultural methods that half the 

 zoospores gave rise to female and half to male plants. 



The investigations of these authors proved conclusively that 

 Monostroma lacked an alternation of generations. Thus in its 

 life cycle this genus departs from Viva and Enteromorpha. Ku- 

 nieda suggested that a separate family, Monostromaceae, should 

 be created for Monostroma, an opinion with which Suneson 

 (1947) and Kylin (1947) concur. In fact, Kylin (I.e.) even sug- 

 gested that the Monostromaceae be removed from the Uvales to 

 the Ulotrichales, which in general are characterized by the type 

 of life cycle shown by Monostroma, although in his recent work 



