1925] SetcheU-Gardner : Melanophyceae 609 



obliterated. Such specimens are parti}" responsible for the report of 

 Laminarkt dermatodea on our northwest coast. Griggs (1907) looks 

 upon this species as of a more simple type than can be adopted by other 

 students of the plant. 



TRIBE 3. AGAREAE kuetz. (lim. mut.) 



Members of the Laminariaceae having blades, either longitudinally 

 ribbed or perforated, or both. 



Kuetzing, Phyc. Gen., 1843, p. 347; Setchell, Kelps of the U. S. 

 and Alaska, 1912a, p. 153. 



Key to the Genera 



1. Adult fronds simple; blades bilaterally symmetrical 2 



1. Adult fronds branched; blades not bilaterally symmetrical 



45. Thalassiophyllum (p. 613) 



2. Rib single; perforations numerous and constant 46. Agarum (p. 614) 



2. Ribs several; perforations frequent, but never constant 



44. Costaria (p. 609) 



44. Costaria Grev. 



Holdfast of branched hapteres ; stipe variable in length usually 

 flattening above ; blade with longitudinal percurrent ribs, each pro- 

 jecting on one side only and alternating on the two surfaces, bullate 

 and not rarely perforate, mucilage ducts absent from both stipe and 

 blade ; sori broad, distributed over most of the blade. 



Greville, Alg. Brit., 1830, p. xxxix. 



The genus Costaria was founded by Greville {he. cit.) to receive 

 a single species, C. Turneri Grev., dedicated to Dawson Turner, who 

 had previously (1819, p. 72, pi. 226) described and figured it as Fucus 

 castatus. Greville also quotes as a synonym the Laminaria costata of 

 Agardh (1820, p. 109 and 1824, p. 269). 



The members of this genus, as at present known, are confined to 

 the waters of the Pacific Ocean, and largely on the North American 

 coast. They are closely related to the species of Agarum, but differ 

 in number, breadth, and structure of ribs, as well as in constancy of 

 perforations. 



