No. 505] KELPS AND RECAPITULATION THEORY 27 



presence the plant is practically possessed of a new basal 

 meristem supplementing and to a certain extent supplant 

 ing the primary meristem. Once established in a favor- 

 able situation, a plant may therefore maintain itself in- 

 definitely, casting off old branches and developing new 

 ones continuously. 



Because of the close similarity of the young stages of 

 Egregia and HedophyUum sessile it will be of interest to 

 add a short description of the latter. It has already been 

 the subect of considerable study by Setchell, who has pub- 

 lished ('05) a discussion of its development well illus- 

 trated by figures. His paper, however, was written from 

 another point of view than the present, namely, the rela- 

 tionships of HedophyUum sessile to the other species of 

 HedophyUum and to Agarum and Thalassiophyllum. 

 Since from this standpoint the very young forms of Hedo- 

 phyUum are not important, Setchell was not particular to 

 obtain plants less than about 5 cm. in length. But for a 

 comparison with Egregia the younger forms are of the 

 most interest. This species 2 is extremely abundant at 

 the Minnesota Seaside Station, outnumbering in individ- 

 uals any other kelp present on that coast. It grows at the 

 highest level occupied by the kelps, and in various situa- 

 tions as regards wave action. 



Vefy young plants of HedophyUum are difficult to dis- 

 tinguish with any certainty from Egregia and from the 

 various species of Laminaria growing in the same locality. 

 HedophyUum is, however, much more abundant in adults 

 and juvenile forms, and as the specimens selected were 

 taken from beds composed mostly of HedophyUum, the 

 probabilities are greatly in favor of a correct determina- 

 tion. The youngest plant (Fig. 5) measured approxi- 



D. HedophyUum 



2 Though Puget Sound is given as th< 

 ican species, HedophyUum subsessile, I 



! to satisfy myself 

 e like those which 



