CULTURE AND MORPHOLOGY ^ 89 



tyosiphonales these zooids form plethysmothalli which sooner or 

 later produce sporophytes as lateral outgrowths. In certain mem- 

 bers of these two orders the life history thus includes two kinds 

 of filamentous plantlets— gametophytes and plethysmodialli— in 

 addition to the conspicuous sporophytic phase upon which the 

 name of the species is based. 



For a long time the method of survival of ephemeral brown 

 algae constituted a perplexing problem, and it was only with the 

 advent of cultural studies that it was learned that these algae per- 

 sist in a filamentous condition during their period of absence 

 from the flora of a given region. 



Although the system of classification of the orders and of many 

 of the families of the Phaeophyta appears to be based on reason- 

 ably secure foundations, large gaps remain in our knowledge of 

 the life cycles of these algae. 



Many of the genera in the orders Ectocarpales, Chordariales 

 and Dictyosiphonales are in particular need of study. To mention 

 but one example, in the family Myrionemataceae of the order 

 Chordariales only one species, Myrionema strangulans Grev., has 

 been investigated (Kylin, 1934). It was found to possess an alter- 

 nation of heteromorphic generations and on this basis the entire 

 family, which includes a comparatively large number of algae, 

 was placed in the Chordariales. It is not unlikely that some of 

 the forms will be found to possess an alternation of isomorphic 

 generations and hence show themselves as belonging to the Ecto- 

 carpales. 



In the Sporochnales, the peculiar parthenogenetic (?) devel- 

 opment of the egg, in the two species that have been investigated 

 thus far (Sauvageau, 1926, 1927), is a matter which calls for 

 further study. 



The preceding account summarizes the main outlines of our 

 present knowledge of the life cycles of brown algae. It has also 

 been pointed out that much of this knowledge was obtained from 

 cultural studies, and it was shown how this information has been 

 utilized in the establishment of a new system of classification. In 

 concluding my remarks on brown algae it may be of interest to 

 refer briefly to two papers by Schreiber that illustrate particularly 



