155 



EISENIA ARBOEEA Aresch. 



By William Albert Setchell. 



(Concluded from page 133.) 



Development. 



A. Earliest Stages. 



The writer was very fortunate in obtaining a number of 

 young fronds representing a considerable variety of stages 

 of development, growing just below low water mark, at Dead 

 Man's Island, which lies at the entrance to San Pedro 

 Harbor, during Christmas week of 1895-96. None of the 

 specimens, however, were young enough to show any trace 

 of a one-layered primitive blade such as certainly exists in 

 all the LaminariacesB whose early stages of development 

 have been investigated. 



The smallest plant collected is about 6 cm. high. It has a 

 short stipe of about 4 mm. in length, one or two very short 

 hapteres, and an ovate-lanceolate blade whose widest portion 

 measures about 2.4 centimeters. 



The short stipe is cylindrical and the lower margins of the 

 blade are absolutely smooth, while the apex is decidedly 

 eroded (cf. PI. V, fig. 1). These plants, together with several 

 others ranging up to about 11 cm. in length, present the 

 same appearance as young plants of species of Laminaria 

 saccharina or more nearly perhaps those of the digitate sec- 

 tion of the same genus. The blades of the largest of these 

 specimens, however, begin to show a few coarse transverse 

 wrinkles. 



B. First Appearance of Pinnules. 



A specimen measuring about 13 cm. in length shows one 

 or two tooth-like projections upon the lower margins of the 

 blade near its confluence with the stipe (cf. PI. V, fig. 2). 

 In slightly older specimens several of these teeth are present 

 upon the basal margins of the leaf on both sides of the 

 stipe and as the specimens increase in size and age, these 

 outgrowths from the base of the blade become even larger 



Ebythea, Vol. IV., No. 11 [7 November, 1898]. 



