I9i6] ROE—SPLACHNIDIUM 



405 



size of the organ, its unilocular nature, its single wall, the number 

 of spores contained, the size of the spore, and the persistent empty 

 case. On the basis of these features there is no reason why Splach- 

 nidium may not equally well be considered as having unilocular 

 gametangia containing isogamous gametes. This would give to 

 Splachnidium a primitive position among the Fucaceae, but would 

 offer for the Phaeophyceae a link in the phylogenetic sequence 

 comparable to the position occupied in the Chlorophyceae by such 

 plants as Ulothrix. 



Moreover, in the Fucaceae the oogonia and antheridia are 

 unilocular, no permanent walls separating the gametes. Also 

 Drew (2) has reported conjugation of isogamous gametes in 

 Laminaria digitata and L. saccharine. "The resulting zygospore 

 divides and gives rise to a chain of cells which may represent the 

 2X generation, and this in turn gives rise to the Laminaria plant, 

 which represents the gametophyte, or x generation." His observa- 

 tions have as yet neither been verified nor disproved. 



Recently Sauvageau (15, 16) has concluded from his investiga- 

 tions that Sacchorhua (and probably all Laminarias) presents a 

 heterogamous sexuality with alternation of generations. The 

 large plant is the sporophyte bearing uniform sporangia, and each 

 sporangium develops like zoospores "which after transformation 

 into embryospores become male gametophytes or female game- 

 tophytes of microscopic size and independent for life. The oosphere 

 expelled from the female gametophyte, then fertilized, germinates 

 at once and develops the plant of Laminaria." 



In the contents of the reproductive sacs, therefore, as well as 

 in form and origin of the conceptacles and in vegetative growth, 

 Splachnidium is intermediate between the Fucaceae and the 

 Laminariaceae. There seems to be no justification for establish- 

 ing a separate family (10) with its main character "reproduction 

 by spOres contained in sporangia which are borne within 

 conceptacles." 



Further investigation will doubtless show a much more intimate 

 connection between the Laminariaceae and Fucaceae than is at 

 present recognized. Splachnidium may be placed with either 

 group, since it has features common to both. Perhaps the presence 



