PROGRESS AND ACHIEVEMENTS IN PHYCOLOGY 557 



tioning as gametangia, and others on diploid plants and functioning as 

 zoosporangia. The diploid plants frequently also form unilocular sporangia. 

 Meiosis occurs in the unilocular sporangia, as had previously also been shown 

 by Yamanouchi with reference to Zanardinia and Cutleria and by Kylin 

 (1918) with reference to Chorda. No reduction divisions occur in the pluri- 

 locular sporangia of diploid plants, and the zooids produced in them germinate 

 directly. 



Knight (1923) showed that the life history of Pylaiella includes an alterna- 

 tion of isomorphic generations. She (1929) was unable, however, to demon- 

 strate an alternation of generations in Ectocarpus. Contrary to the long-held 

 belief that the zooids produced in the unilocular organs were zoospores, she 

 claimed that in British waters the zooids from the unilocular organs of E. 

 siliculosus function as gametes. In this region there consequently existed only 

 diploid plants. She repeated the observations of Berthold and others at Naples 

 and established that in that area the plants were haploid and their plurilocular 

 organs were gametangia. 



Papenfuss (1933, 1935), studying Ectocarpus siliculosus in the region of 

 Woods Hole, confirmed the observations of Knight that this species includes 

 haploid plants which form only plurilocular organs and diploid plants which 

 form both unilocular and plurilocular organs. He was unable, however, to 

 confirm her observations regarding the gametic nature of the zooids from the 

 unilocular structures. Instead, he found that E. siliculosus exhibits an alterna- 

 tion of isomorphic generations. F0yn (1934) has established the occurrence 

 of a similar cycle in Norway, 



Several other investigators have claimed a gametic role for the zooids from 

 the unilocular organs of diverse brown algae. Although such behavior is 

 theoretically possible, the evidence presented for the alleged instances of 

 conjugation between these swarmers is not convincing. It would indeed be 

 remarkable if gametes could be produced by the diploid as well as the haploid 

 generation of a plant such as Ectocarpus siliculosus. 



In 1915 Sauvageau made the epoch-making discovery that Saccorhiza 

 bulbosa, a member of the Laminariales, possesses an alternation of hetero- 

 morphic generations comparable to that of ferns. The familiar macroscopic 

 plant was shown to be the sporophyte. The zoospores formed in its unilocular 

 sporangia produce microscopic, filamentous gametophytes which are dioecious 

 and form oogonia and antheridia. 



This very significant discovery by Sauvageau, which was made on the 

 basis of cultures, aroused a great deal of interest in the brown algae. It was 

 evident that the cycle of development of many of these algae could not be 

 ascertained unless they were grown in culture. It was also clear that rich 

 rewards were in store for those who would follow his approach to problems 

 relating to the life histories of the brown algae. We today know the broad 

 outlines of the life history of a large number of brown algae. With the ex- 



