404 BOTANICAL GAZETTE [November 



In establishing a new family Mitchell and Whitting (io) 

 summarize their reasons in the following statement (p. 8) : 



While, then, the characteristics of Splachnidium rugosum are such that it 

 can be placed in no existing natural order of the Phaeophyceae, its nearest 

 allies appear to be the Fucaceae on the one hand and the Laminariaceae on the 

 other. In its vegetative structure, in the nature of its thallus, and in the exist- 

 ence of conceptacles, Splachnidium bears a resemblance to the Fucaceae; 

 it differs from them, however, in its mode of growth, the former increasing by 

 means of an apical meristem, while the growth of the latter is due to division 

 of an apical cell. In the presence of an apical meristem Splachnidium 

 approaches the Laminariaceae, but at the same time there is no plant in this 

 order which has a cell corresponding to the remarkable cell found at the apex 

 of the main axis and lateral branches of Splachnidium. In its reproduction it 

 is allied to the Laminariaceae, and the production of sporangia within con- 

 ceptacles might seem to point to a narrower limitation of the fertile sorus of 

 plants of this order, recalling the difference between perithecium and apothe- 

 cium in the fungi. 



As to vegetative growth, the tissue of the thallus of Splachnidium 

 bears an equal resemblance to the Fucaceae and the Laminariaceae, 

 the only essential difference being in origin. Splachnidium and 

 the Laminariaceae are products of a meristem, the former apical, 

 the latter intercalary, according to the evidence of most authorities, 

 and not apical as described by Mitchell and Whitting in the 

 passage just quoted. The Fucaceae, too, are characterized by 

 apical growth of the thallus, but all tissue is the actual result of 

 segmentation of a definite apical cell. In vegetative growth, then, 

 Splachnidium is intermediate between the two groups. 



The presence of conceptacles certainly seems a definite con- 

 necting link with the Fucaceae; and yet some of the Laminariaceae 

 show a tendency to approach this method of reproduction. Smith 

 and Whitting (17) describe deep furrows in Macrocystis and Pos- 

 telsia, which closely resemble conceptacles in form and origin. In 

 this feature, too, Splachnidium is intermediate between the Fuca- 

 ceae and the Laminariaceae. 



Murray (ii, 12) and Mitchell and Whitting (10) conclude 

 that the reproductive sacs of Splachnidium are neither oogonia nor 

 antheridia homologous with those of the Fucaceae, but are spor- 

 angia homologous with those of the Laminariaceae, because of the 



