1920] Setchell-Gardner : Chlorophyceae 165 



1. Derbesia marina (Lyngb.) Kjellm. 

 Plate 15, fig. 3 



Filaments arisiii'z from a creeping base, bright green, 50-7()/x diam., 

 simple or usually with a few lateral branches similar to the axes, 

 continuous l)ut with a short segment separated by partitions near the 

 base of a brancli or occasionally in the axils just above a l)raneh, 

 little smaller than the branch itself and about as long as broad ; 

 sporangia occupying tlie place of branches, ovoid to subspherical, 

 150-250/x long, 90-200/^ broad ; pedicel varying from 30-70^ in length, 

 30-35/x in diameter, about as long as broad; spores 20 or more in a 

 sporangium. 



Alaska to southern California. 



Kjellman, Alg. Arctic Sea, 1883, p. 316 (not of Solier, fide J. G. 

 Agardli, Till. Alg. Syst., 5th part, VIII, 1886, p. 34) ; Saunders, Alg. 

 Harriman Exp., 1901, p. 415; Setchell and Gardner, Alg. N.W. Amer., 

 1903, p. 230; Collins, Green Alg. N.A., 1909, p. 407. Derbesia tenuis- 

 sinm Collins, Holden and Setchell, Phyc. Bor.-Amer. (Exsicc), no. 

 574. Vaucherm marina Lyngbye, Hydr. Daji., 1819, p. 79, pi. 22 A. 



We suspect that the Derbesia vmicheriaeformis of Saunders (1899, 

 p. 3, pi. 350, f. 4 a-d) from "Point Lobos" (really Point Cannel) near 

 Monterey, California, is to be placed rather under I). iiKirina as 

 understood by J. G. Agardh. Saunders describes his species as pos- 

 sessing filaments from 30^ to 40/a broad and elliptical, obovate or 

 pyriform sporangia 140/I, to 200/a long and 50^ to SO/n wide. The 

 sporangia are distinctly pedicellate but the diameter of the pedicel 

 is not given. Judging from his figure 4a, the pedicel is one half the 

 diameter of the filament, or 15/a to 20/a broad. The zoospores, also 

 judging from the same figure, number decidedly more than twenty. 

 The branching is represented as dichotomous. Saunders, also, in the 

 Algae of the Harriman Expedition to Alaska (1901, p. 415) refers 

 a plant from Yakutat Bay to D. vmicheriaeforniis, but did not oliserve 

 mature zoosporangia. 



2. Derbesia Lamourouxii (J. Ag.) Sol. 



Filaments arising from a creeping ba.se, a few centimeters to 2 dm. 

 high, 100-600/A diam., dark green, rather stiff, sometimes simple, some- 

 times with more or less numerous irregular branches; sporangia 

 spherical, 300-550/a diam., sessile or on sliort and slender pedicels. 



Southern California. 



