606 University of California Publications in Botany [Vol.8 



10, pi. 38, fig. /. Laminaria nigripcs J. G. Agardh, Spetsb. Alg., Till. 

 1868, p. 29. Laminaria atrofidva J. G. Agardh, Groenl. Alg., 1872, 

 p. 16. Laminaria fissilis J. G. Agardh, De Lamin., 1867, p. 18. 



After trying in vain to find definite lines of cleavage between the 

 Arctic species, L. nigripcs J. Ag., and L. atrofidva and the North 

 Atlantic L. platymeris De la Pyl., all three digitate species, with 

 mucilage ducts in the flattened stipes, Setchell (1912a, p. 151) decided 

 to unite them. In a similar fashion he found it impossible to separate 

 satisfactorily Laminaria fissilis J. Ag. and L. Bongardiana P. and R. 

 of the North Pacific. He found also that the two groups of North 

 Atlantic (Arctic) and North Pacific had no definite characteristics to 

 segregate one from the other. He consequently, combined them all 

 under the oldest tenable name, viz., L. platymeris De la Pyl. 



Each of the components of this general group shows form varia- 

 tions as to length of stipe, thickness of stipe, degree of flattening or 

 compression of stipe, and length, breadth, shape of base, and degree 

 of splitting of blade. The following sets of form names may illustrate 

 this variation : f . taeniata, f . oblong a, f. elliptica, and f . reniformis as 

 to shape and base of blade ; f. brevipes and f. longipes as to varying 

 length of stipe ; f. complanata, f. eompressa, and f. sub teres, as to com- 

 pression or flattening of the stipe. Most forms may be better designated 

 by combinations of the foregoing names than by any single one of them. 



tribe 2. CYMATHAEEEAE s. and g. 



Members of the Laminariaceae (in sensu restrict) having the 

 blades provided with one or more longitudinal folds. 



Key to the Genera 



1. Fold single, broad, median 42. Pleurophycus (p. 606) 



1. Folds several, narrow 43. Gymathaere (p. 608) 



42. Pleurophycus Setchell and Saunders 



Holdfast of numerous branching hapteres; stipe simple ; blade long, 

 undivided, with a single median, longitudinal, rather broad, shallow 

 fold and with broad, at times ruffled, margins ; sori narrow on both 

 surfaces of the median fold ; mucilage ducts absent from both bladder 

 and stipe. 



Setchell and Saunders MS., in Setchell, Notes on Algae I, 1901, 

 p. 123, in Saunders, Alg. Harriman Exp., 1901, p. 427 (description). 



