248 University of California l^uhlications in Botany T^^ot- 8 



1. Enteromorpha groenlandica (J. Ag.) S. and G. 



Frond filiform, tubular, cylindrical, up to 15 cm. long, from a very 

 slender base expanding to 1 mm. diameter; apex broken only at exit 

 of spores ; cells in the lower part loosely arranged in twos and fours, 

 roundish angular; cells in the upper part more evenly distributed, 

 more or less loosely set ; in cross section the membrane 25-35/i. thick ; 

 the cells radially elongate, 2-4 times as long as broad ; in the younger 

 parts the central cavity filled with a gelatinous substance which dis- 

 appears as the plant becomes older; spores or gametes forming first 

 at the sununit of the frond, and developing successively in lower cells. 



On small boulders in the middle littoral belt. Alaska (Bay of 

 Unalaska and Kukak Bay): 



Setchell and Gardner, Phyc. Cont. I, 1920, p. 280. Monostroma 

 groenlandicuni J. Agardh, Till Alg. Syst., part III, 1883, p. 107, pi. 3, 

 f. 80-83; Collins, Green Alg. N. A., 1909, p. 208; Saunders, Alg. ITar- 

 riman Exp., 1901, p. 410; Setchell and Gardner, Alg. N.W. Amer., 

 1903, p. 208. 



Enteromorpha groenlandica has always been puzzling as to its 

 proper placing. While technically it may seem to belong to the genus 

 Monostro^na, under which it was originally described, more properly 

 than to any other genus of the Ulvaceae, yet its slender, filiform habit 

 certainly more closely resembles that of some species of Enteromorpha. 

 From Enteromorpha, however, it differs in not having its cells set 

 sufficiently closely together to be parenchymatous in appearance. It 

 is at first solid, becoming hollow only late, but never rupturing longi- 

 tudinally and opening out into a membrane as do the characteristic 

 species of Monostroma. Certain species of Enteromorpha show a 

 tendency towards abundance of intercellular jelly at times, while 

 certain species of Monostroma are parenchymatous. It seems best 

 to us, therefore, to transfer this species to Enteromorpha. 



The plants of the North Pacific Ocean, as Collins (1909, p. 209) 

 states, have decidedly smaller cells than those of the North Atlantic, 

 measuring 8-10/a in diameter, as against 12-16/a as seen superficially. 

 It seems, therefore, to constitute a different form. 



The species is a summer plant of the Upper Boreal Zone, invading 

 the Lower Boreal and North Temperate Zones only as a short-lived 

 plant of the springtime when the waters are colder than in the summer. 

 This intrusion happens, so far as we have evidence, only on the eastern 



