PAPENFUSS: CLASSIFICATION OF THE ALGAE 169 



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

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

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

 the zooids from the unilocular organ were zoospores, she claimed that at least 

 in British waters the zooids from the unilocular organs of Ectocarpus func- 

 tioned as gametes. In this region there thus existed only diploid plants. She 

 repeated the observations of Berthold and otliers at Naples and found that in 

 that area the plants were haploid and their plurilocular organs were gamctangia. 



Papenfuss (1933, 1935), working at Woods Hole, Massachusetts, confirmed 

 the observations of Knight that Ectocarpiis included haploid plants which bear 

 only plurilocular organs and diploid plants which form both unilocular and 

 plurilocular organs. He was unable, however, to confirm her observations re- 

 garding the gametic nature of the zooids from the unilocular organs. Instead, 

 he found that Ectocarpus exliibited a regular alternation of isomorphic genera- 

 tions. The observations of Papenfuss were confirmed by F0yn (1934) working 

 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 theo- 

 retically possible, the evidence presented for the alleged instances of conjuga- 

 tion between these swarmers is not convincing. It would indeed be remarkable 

 if an organism, such as Ectocarpus siliculosus, could form gametes on the diploid 

 as well as the haploid generation. 



In 1904 AVilliams demonstrated the occurrence of an alternation of isomor- 

 phic generations in Dictyota and in 1915 Sauvageau made the epoch-making 

 discovery that Saccorhiza hulhosa, a member of the Laminariaceae, possesses an 

 alternation of heteromorpliic generations comparable to that of ferns. The fa- 

 miliar macroscopic plant was found to be the sporophyte. The zoospores formed 

 in its unilocular sporangia give rise to microscopic, filamentous gametophytes 

 which are dioecious and produce oogonia and antheridia. 



This very significant discovery of Sauvageau, which was made on the basis of 

 cultures, created a great deal of interest in the brown algae. It was evident that 

 the complete cycle of development of many of these algae could not be ascer- 

 tained 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 brown algae. He himself retained leadership in this fruitful 

 field until his death in 1936. (For a list of his many publications see Dangeard, 

 1937.) 



The knowledge that has accumulated during the past fifty years has natu- 

 rally had far-reaching effects on the classification of the Phaeophycophyta. 



Although Lamouroux (1813), C. Agardh (1817, 1824), and Harvey (1836) 

 had recognized the autonomy of the brown algae, each of them had included in 

 the group certain dark-colored red algae or had assigned representatives of the 

 group to other major taxa. 



In 1848 J. Agardh published the first volume of his Species genera et ordines 

 algarum, a volume devoted exclusively to the brown algae. The Phaeophyco- 

 phyta were segregated by J. Agardh into seven tribes (also referred to by him 

 in different places as families or orders), six of which were first recognized by 

 Greville (1830) and Harvey (1836). It is noteworthy that each of these seven 



