Stichococcus 163 



Hormiscia subtilis DeToni Syll. Alg. I : 159. p. p. 1 



Filaments long, often forming extended bright green, lubricous 

 masses ; cells cylindrical, not constricted at the dissepiments, 

 5—6.5// (rarely 8//) in diameter, 1-3 times as long; cell-wall 

 thin; chromatophore elliptical, containing a rather small pyrenoid. 

 Zoospores are formed freely at certain times ; the cells break 

 apart for vegetative propagation less readily than in any other 

 species (j>l. 2i y f. 10-13). 



Exsic: Phyc. Bor. Am. (Ulothrix subtilis), 614.A. Medford, 

 Mass., June, 1892; 614.B. Melrose, Mass., August, 1898 (F. 

 S. Collins); 614.C. Nantucket, August, 1895 (W. A. Setchell). 



On moist or dripping cliffs, on rocks of cascades, in watering- 

 troughs and in quiet waters. 



Vermont : St. Johnsbury, August to October (642, 647). 



Massachusetts : Melrose, April (549). 



Connecticut : Thomaston, September (494), May (543) ; Ply-' 

 mouth, October to May (665, 521, 523); Watertown, May (561, 

 562). 



New York: Botanical Garden, April (534B); Morningside 

 Park, April (264, 28 5 B, 32 1 B, 353), May (425), June (616), 

 November (512); Central Park, June (617, 637A). 



New Jersey : Long Branch, September (477) ; Undercliff, 

 Bergen county, December (232), April, May (528C, 368, 427A, 

 576). 



Pennsylvania : Bethlehem, June (444). 



The filaments of this species show a greater stability than 

 those of any other, with the possible exception of S. rivularis. 

 Only rarely are zoospores seen ; sometimes in warm weather they 

 are developed rather freely. The plant is capable of enduring the 

 greatest extremes of dryness or immersion ; it vegetates on rocks 

 until their faces become quite dried up in the summer, and, on the 

 other hand, it presents a luxuriant growth amid the icy waters of 

 a watering-trough or in a frozen cascade in winter. Several fila- 

 ments from drying rock appeared to be forming akinetes in prepa- 

 ration for the summer, but where the water supply is favorable, 

 probably the plant continues to grow during the whole year. 



This species perhaps is the one most nearly related to Ulo- 

 thrix, yet its chromatophore and pyrenoid, in the state of active 

 growth, always have the typical Stichococcus character. Further- 



