166 ULOTHRICACEAE 
In cascades on oblique surfaces of rocks dashed with spray or 
covered by a thin sheet of water. Melrose, Mass., 28 April, 1901 
(548). Undercliff, New Jersey, و‎ April, 16 April, 1900 (279, 
307), 20 May, 1901 (575). 
The conditions in these two stations are exactly similar. On 
certain rocks, the plants form a cespitose covering presenting the 
appearance of a short Myxonema. By this habit and by its yel- 
lowish green color, this species is always distinguishable to the 
naked eye, from the long, darker green skeins of Stichococcus 
subtilis, which frequently hang from adjacent rocks. The speci- 
mens from both stations showed, in the most marked degree, the 
tendency to dissociation of the filaments. Within a few hours after 
being removed from the rapid current on the rock, a very large: 
proportion of the filaments had broken up into single cells or 
chains of two to four. 
Our American specimens show a distinct, though not strongly 
marked torulose character of the filaments, which is not mentioned 
by Gay, while the geniculate character emphasized by him does 
not appear prominent. However, as the identification of Mr. 
Collins’ specimen was made by Professor Wille, we do not feel 
justified in making a different disposition of the plant without 
further evidence from the author of this species, and this we have 
been unable to obtain. 
7. Stichococcus rivularis (Kütz.) 
Hormidium rivulare Kitz. Phyc. German. 192. 1845. 
Ulothrix rivularis Kitz. Spec. Alg. 346. 1849; Tab. Phyc. 2: 
pl. 86, f. 2. 1851; not Alg. Dec. 49. 1833 (= Rhizoclonium). 
Rabenh. Flor. Eur. Alg. 3: 366. 1868. Wolle, F. W. Alg. 
136. ۸. FIS. J. 6-8. 1887. 
Ulothrix rivularis var. cataracta Wolle, ibid. pl. 118. f. 29-33. 
Hormiscia rivularis DeToni, Syll. Alg. 1: 167. 1889. 
Filaments forming somewhat elongated bright green tufts, fre- 
quently geniculate, but not easily breaking apart, composed of 1-3 
cells, developing rhizoidal hooks from the terminal cells and from 
those of the knees ; cells somewhat constricted at the dissepiments, 
rather thick-walled, 8-11 rin diameter, 1-2 times as long ; chromat- 
ophore orbicular to elliptical or rhomboidal, with clear-cut out- 
line, containing a large pyrenoid (ai 22, f. 70-13). 
