FRESH-WATER ALG^ OF THE UNITED STATES 29 



have referred to N. verruoosum with some little hesitation. Soine of the fronds 

 were smoothish, others very decidedly warty. My specimens are old plants, 

 which have become hollow by the discharge of their internal contents. It is pos- 

 sibly on this account I have not been able to verify the minute description given 

 by Professor Rabenhorst. As the latter may not be accessible to some of those 

 who consult these pages, I append the latter part of it, which differs from that 

 given by myself from the American plants. 



" Trichomatibus flexuoso-curvatis, quasi triplici ordine ; centralibus parcioribus, 

 laxissime implicatis, apices versus plus minus attenuatis, articulis oblongis, sub- 

 distantibus, periphericis densius ssepe densissime intricatis, basi baud raro cellulis 

 biseriatis, articulis globosis, arete connexis, extremis (nonnisi in thallo vetusto 

 occurrunt) subflagelliformibus, articulis oblongis, cylindraceis sphsericisque simul 

 immixtis, distantibus; cellulis perdurantibus sphsericis interjectis terminalibusque, 

 nonnunquam pluribus simul seriatis articulorum diametro duplo triplove majoribus." 



According to Professor Harvey (Nereis Bor. Amer., part iii. p. 114), this species 

 has been collected by Dr. Lyall in pools of fresh water. Isle of Disco, and at 

 Beechey Island, Arctic Begions; also by Mr. Fendler at Sante Fe, New Mexico. 



IV. alpinum, Ktz. 



N. rupestre, immersum ; thallo suborbiculare, erecto, membranaceo, ad ^=| unciam lato, ad 

 lineas duas vel tres crasso, tenaci, saturate olivaceo-fusco, Isvi, ssepe rugoso-plicato, cum mar- 

 gine integro at plerumque incrassato ; trichomatibus varie curvatis, laxe vel nonnihil dense 

 implicatis; articulis fuscisvel dilute terugineis plerumque globosis, ssepe snbtiliter granule tls, 

 arete connexis; cellulis perdurantibus sphsericis plerumque articulorum diametro paulo ma- 

 joribus, interdum subsequalibus, interjectis vel termihalibus. 



X>mm.— Artie, vegetativ. .00016"— 00023" ; cell. perd. .00026. 



Syn.^^" N. alpinum, Ktz. Phycol. General., p. 206, No. 10." Rabenhoest, Flora Europ. 

 Algarum, vol. ii. p, lli- 

 " N. Sutherlandi, Dickie." Harvey, Nereis Boreali Americana, part iii. p. 114. 

 " N. cristatum, Bailey." Harvey, Nereis Boreali Americana, part iii., 1857, p. 114. 

 Growing attached by its margin to the^ rocks in running water; thallus suborbicular, erect, 

 membranaceous \ — | an inch high and 1 — 3 lines thick, very tenacious, deep olive-green, 

 smooth, often rugosely plicate especially at the base, with the margin entire, rounded, and 

 mostly thickened; filaments variously curved, laxly or somewhat densely interwoven; arti- 

 cles fuscous or greenish, mostly globose, often finely granulate, closely connected; heterocysts 

 spherical, generally a little larger than the ordinary cells, sometimes about equal to them, 

 interspersed and terminal. 



RemarTcs.—Th\s interesting little plant was found in the mountain rivulets 

 near West Point, New York, by the late Prof. Bailey, and received from him the 

 specific name cristatum, first published in Harvey's work on the North American 

 Algffi. I have myself seen it growing in very great abundance in rapid mountain 

 streams in the central portions of this State. It is doubtless, therefore, an inhabi- 

 tant of the whole Alleghany range. In the low country, east or west of these 

 mountains and their outlying hills, I do not know of its having been found. I have 

 very recently received specimens of a nostoc from Sereno Watson, Esq., undoubt- 

 edly belonging to this species, which were collected by himself, in cold streams in the 

 Clover Mountains, Nevada, at an altitude of 11,000 feet. Under the name of M. 



