160 EEYTHEA. 



blade and resemble very closely the simpler Laminarise. 

 Then the pinnules begin to appear and gradually give the 

 frond the appearance of an Ecklonia. Finally the especial 

 characteristics of the genus develop by the thickening of 

 the bases of the blade, the splitting and separation of the 

 meristematic regions, and the various accompanying second- 

 ary changes which lead to the productiou of the arms and 

 the ligules with their sporophylls. 



The most interesting thing in the morphology and develop- 

 ment of Eisenia is without question the branching. It is the 

 only member of the Eckloniese as far as is kaowu, which 

 branches, and the branches in origin, and portion of the 

 plant concerned, can hardly be homologized with any of the 

 normal branches of other members of the Laminariacese. 

 The species of only one other genus of the Alariideae 

 (or LaminariacetB with sporophylls arising as outgrowths 

 from the frond) possess branches, viz. Egregia, and the 

 branches in the species of that geuus arise in quite another 

 fashion. The nearest approach to the method of branching 

 in Eisenia is to be found in the Lessoniide^e and in the sub- 

 tribe Lessoniese. The branching here is dichotomous and 

 arises at the transition-place where the meristematic tissue is 

 completely separated into two longitudinal halves. But the 

 behavior of the meristematic tissue, from which growth in 

 length proceeds, appeal's to be even more complex in Eisenia 

 than in any of the Lessonioid genera, because in Eisenia there 

 occurs, apparently, first a transverse splitting in which the 

 portion belonging to the stipe is separated from that belong- 

 ing to the blade. This kind of differentiation or separation 

 occurs in no other member of the LaminariaceaB as far as the 

 writer knows. It is the rule in all the other branching, as 

 well as the unbranching, forms, that stipe and blade possess a 

 common meristem at the transition-place. New meristems 

 may arise, as in Egregia and in Thalassiophyllura, giving rise 

 to branches of the stipe and new blades, but in every case 

 each meristem adds to stipe upon the one side and to blade 

 upon the other. 



