Distribution of the Laminar iacece. 341 



northern portions of the Pacific Ocean. It differs decidedly in 

 general appearance from Agarum Turneri, yet in its essential feat- 

 ures comes very close to it. It has the same peculiar perforations 

 in the blade and they arise in essentially the same fashion as in 

 Agarum.^ The blade unrolls itself from a scroll-like transition-place 

 as in Agarum, only in Thalassiophyllum, there is only one, very 

 large scroll and the resulting blade is one-sided and fan-shaped with 

 a cuneate base. As the blade unrolls itself it dies away on the free 

 margin and leaves behind itself upon the stipe a spirally twisted 

 ridge-like scar which is different from anything found in any other 

 species of the Laminariacese unless it be the scar on the stipe of 

 Arthrothamnus Kurilensis, Rupr. which is mentioned below. 



The frond of Thalassiophyllum is branched, but the branches do 

 not follow a regular order as they do in JOessonia nor do they arise 

 by any similar process, but originate as proliferations from the mar- 

 gins of newly formed perforations at the transition-place.^ 



Costaria, Grev. — This genus also contains a single species, C. 

 Tumeric Grev. which is peculiar to the northeastern portion of the 

 Pacific. The stipe is short and the blade is broadly ovate. The 

 stipe expands gradually into the blade in the younger specimens but 

 in the older specimens the base is decidedly cordate.^ There are no 

 scrolls at the base of the blade, but the transition-place is unmodified 

 and is plane except where the ribs are forming. These ribs run 

 longitudinally through the blade and are five in number. Both 

 Agardh^ and Areschoug^ call them "plicae" and explain that they 

 project on one surface of the frond and are hollowed in on the other. 

 Furthermore they both agree that the stipe is 5-striate and that the 

 " plicae " of the blade are continuations of these striae of the stipe. 

 The writer has had the opportunity, through the kindness of Prof. 

 W. G. Farlow of Cambridge, Mass., and of Mr. F. S. Collins of 

 Maiden, Mass., to examine both old and young herbarium specimens 

 and is indebted to Dr. C. L. Anderson of Santa Cruz, Cal., for a fine 

 series of younger specimens preserved in moderately strong alcohol. 

 The examination of these specimens failed to show the striae on the 

 stipe and also has shown that while the so-called "plicae" project 

 on one surface of the blade owing to a thickening in the cortical 



1 Cf. Rosenljial, Flora, Bd. 48, p. 140, 1890. 



2 Cf. Rosenthal, loc. cit , p. 140, PL 7-8, f. 33a and 34a. 

 ■^ Cf. P. & R., III. Alg., PI. 24. 



^ De Laminarieis, p. 3. ^ Qbs. Phyc , Pt. 4, i)p. 10-20. 



