252 The American Naturalist. [March, 



who support the hypothesis of a marine origin. Now that it is settled 

 that the Gulf Stream is n..t a single narrow stream issuing from the 

 (iulf of Mexico, but an accumulation of converging currents sweeping 

 past the coasts of the Antilles and through the adjoining seas, it is 

 obvious that the quantity of algae carried away must be much greater 

 than it could have been were the old hypothesis of the origin of the 

 Gulf Stream correct. Dr. Kriimmel makes an opproximate calcula- 

 tion as to the time occupied by the alga- in reaching the Sargasso 

 Sea. A fortnight after reaching the Gulf proper, the weed would, at 

 the rate of two knots an hour, reach the latitude of Cape Hatteras. 

 From that point its onward motion is slower, and it takes about five 

 months and a half for it to reach west of the Azores. After reaching 

 the Sargasso Sea the weed continues to move slowly, until, becoming 

 heavier as it grows older, it gradually sinks to make way for fresh 

 supplies. (Proceeds. Roy. Geog. Soc, Oct., 1891.) 



Ferns of the Black Hills.— Last July while collecting in the 

 Black Hills of South Dakota the following ferns were recorded. My 

 collecting field was in the central portion of the Hills in the vicinity 

 of Harney's Peak. About the same time Professor Williams of 

 Brookings, S. D. visited the eastern part of the Hills, and made a few 

 notes which I add to mine. This list is interesting inasmuch as it is 

 much larger than any yet made for this region, including several 

 species not hitherto known to grow this far west. 



Poly-podium vulgare L.— Abundant on the rocks in and about 

 Harney Glen, on the side of Harney's Peak. 



Adiantum pedatum L.— Reported on good authority from near Hot 

 Springs, but no specimens were secured. 



Pteris aquilina L— Specimens were seen, but not collected, between 

 Hill City and Dead wood. 



Cheilanthes lanuginosa Nutt.— On the rocks at Custer ; Professor 

 Williams collected it at Rapid City, also. 



Pellcea atropurpurea Link.— On the rocks at Custer. Collected at 

 Rapid City also by Professor Williams. 



Asplenium trichomanee L.—On the rocks at Custer, and in tne 

 ravines on Harney's Peak. 



Asplenium septentrionale Hoffin.— In the crevices of rocks at < 'u?u% 

 and in Harney Glen. This is a most curious fern, resembling a tuft 



