March, 1907.] Cymathere, a Kelp from the Western Coast. 93 



The smallest specimen which could be certainly identified 

 was about 7 mm. long (fig. 4). In this the stipe was only very 

 slightly longer than in the smaller specimen, being still less than a 

 millimeter while the lamina had become much longer. From 

 this period on through life the species is characterized by a long 

 narrow lamina on a very short stipe. In the center of the lamina 

 has appeared a band of tissue several cells in thickness, which 

 extends from the transition region, where it narrows into the 

 stipe, in an oblong patch through the middle of the blade to 

 within about 2 mm. of the tip. 



This thicker area soon cuts off and separates the original 

 thinner portion from the growing point in the transition region 

 and pushes it out into the end of the lamina. This action does 

 not, however, as might be supposed, presage the speedy disap- 

 pearance of the primitive thin region. On the contrary it shows 

 itself able to make good the waste of erosion for a long time and 

 even increases very much in size. At the first appearance of the 

 thicker band its area is only about 6 sq. mm. while in a specimen 

 about 5 cm. long (fig. 8) it covers ISO sq. mm. forming a wide 

 rufile all around the tip of the lamina. It continues to be found 

 on specimens even longer than 200 mm. (225 is the longest of 

 such in my collection) but greatly eroded though still giving 

 evidence of continued growth. The presence of a lamina one 

 cell in thickness has been noticed by Setchell '05 who gives a 

 summary of the cases in which it is known to occur. These are 

 Laminaria saccharina, Saccorhiza dennatodea (Setchell '91) and 

 Alaria escidenta all of which Setchell himself has seen, though 

 the case of Laminaria was earlier described by Reinke and per- 

 haps by Kuetzing whose determination, however, Setchell ques- 

 tions. From these cases Setchell infers that such a stage is 

 common to all of the Laminariaceae. Though not so described 

 by MacMillan '99, Nereocystis has the same manner of growth. 

 The writer has in his collection a plant 4 cm. in length in which 

 the pneumatocyst is just beginning to show as a darkened area 

 slightly different to the touch, and a very faint short depression 

 already marks the beginning of the first split. In this specimen 

 there is a margin extending around the tip and half way down 

 the blade about 1 mm. wide, of thin tissue exactly as in Cyma- 

 there. In Saccorhiza as figured by Setchell '91, the primitive 

 blade persists only till the plant is about 7 cm. long. I am in- 

 debted to Professor Setchell for the information that nearly 

 all the plants from the northwest coast labelled by Harvey 

 Alaria marginata are young specimens of Cymathere, a designa- 

 tion which may well have been suggested by the long persisting 

 remannts of the embryonic lamina. All this would indicate 

 that the large size attained by the one layered lamina in Cyma- 

 there is quite exceptional. 



