A 
84 Rhodora [May 
tions unfavorable to vegetative growth, its absence in the pelagic 
Sargassum is probably due to the uniformity of conditions and steady 
vegetative growth; the Ascophyllum has at any rate not reached that 
state. 
The only other plant to be considered in this connection is a Cysto- 
seira resembling C. crinita Bory, a number of specimens of which were 
found in a lot of S. natans, collected in the North Atlantic by Profes- 
sor F. H. Storer, in August, 1854, on a voyage in a clipper ship from 
Canton to New York.! The Cystoseiras are specially characteristic 
of the Mediterranean, but extend on the Atlantic both north and south 
of the Straits of Gibraltar. Sauvageau,? gives 33 species as occurring 
within this range, and considers the floating plant, while nearest to 
C. crinata, not exactly identical. The only American species of the 
genus is C. Myrica Bory, a very different plant. 
In conclusion:— The predominant species of the Sargasso Sea is 
S. natans (L.) J. Meyen; through long pelagic existence so differen- 
tiated from its original attached ancestor that the latter cannot now 
be identified; of active vegetative growth but propagating only by 
fragmentation, having associated with it a much specialized fauna. 
The Sargassum exists not as a continuous mass, but as scattered patches 
through an area in the North Atlantic bounded by the Gulf Stream, and 
its subsidiaries reaching the coast of Europe, thence south and again 
west to the point of origin in the Gulf of Mexico; fragments may be 
driven by high winds to the shores of New England and Northern 
Europe. 8S. fluitans Börgs. accompanies it, but in less quantity, less 
differentiated, probably more recently, from its attached ancestor, 
which may be S. Hystrix J. Ag. Of equal distribution but in relatively 
minute proportion, Ascophyllum nodosum (L.) Le Jolis is practically un- 
differentiated from the attached plant, but though floating and fruiting 
freely for weeks, probably for months, cannot be considered persist- 
ent in the pelagic condition. Finally there is a sterile Cystoscira, re- 
sembling C. crinita Bory, found once only, its status therefore uncertain. 
Norru EASTHAM, MASSACHUSETTS. 
1 For details of this collection, as also for many interesting remarks on pelagic Sargassum, see 
_ W. G. Farlow, The vegetation of the Sargasso Sea. Proc. Amer. Phil. Soc., Vol. LIII, p. 257, 
1914. 
? C. Sauvageau, À propos des Cystoseira de Banyuls et de Guéthary. Bull, Sta, Biol. Arca- 
chon, 14e année, 1912, 
