1922] Gardner: The Genus Fucus on the Pacific Coast 43 



fronds, the blunt and somewhat fusiform, receptacles, and the dendroid 

 habit certainly suggest its close similarity with f. dendroides. How- 

 ever, I am inclined to keep it distinct on account of its decidedly more 

 robust habit, the practical absence of cryptostomata, the much lighter 

 color than that of the other forms within our region which I have 

 placed with f. dendroides, and the distinctly marginal receptacles. 



Fucus spiralis, although, for modern usage, imperfectly described 

 by Linnaeus, has relatively recently been taken up by a number of 

 algologists to include certain forms on both the European and the 

 American shores of the Atlantic. Kjellman (1883, p. 202) definitely 

 recognized it as a species, segregating, as new, f. borealis. In 1890, 

 however, he changed his conception of the species and named it F. 

 Areschougii, segregating f. nana. De-Toni (1895, p. 207) recognized 

 F. spiralis as a valid species and reduced Kjellman 's F. Areschougii 

 to synonym. Borgesen (1902, pp. 472-477) followed De-Toni, and in 

 a clear discussion reduced also F. platycarpus Thuret to a form of 

 F. spiralis. Howe (1905, p. 581), after having examined the speci- 

 mens in the Linnaean Herbarium supposed to represent Linnaeus' 

 conception of F. spiralis, agrees with Borgesen 's conception with regard 

 to the validity of F. spiralis, considering as the typical form no. 234 

 of Collins' distribution from Maine in the Phycotheca Boreali-Amer- 

 ieana sub F. Areschougii, and recently, in a letter to me, he states 

 that he is inclined to place under this species most of the American 

 plants which have previously passed for F. platycarpus of Thuret. 

 Cotton, in Clare Island Survey, 1912, has kept up the name for certain 

 forms in that locality. It seems thus to be quite well established as a 

 species; the limits of variation, however, and the exact number of 

 forms which should be grouped with it, have not yet been agreed upon. 

 So far as I can learn, the name has not yet been used to designate any 

 Pacific Ocean forms. Forma marginatus, under discussion, has some 

 characters which might well link it with F. spiralis. It has the char- 

 acteristically twisted segments in the upper part of the fronds, and the 

 margined receptacles figured by Borgesen (loc. cit.), but the specimens 

 of spiralis to which I have had access usually show an abundance 

 of cryptostomata emitting fascicles of relatively long paraphyses, 

 deeidedly different in this respect from our plants. They also have 

 shorter and more rounded receptacles and alae wider in proportion to 

 the length of the segments. 



