Myxophyceae 97 



Proc. Biol. Soc. Wash. 21: 154. 1908; American Algae. Cent. VII. Fasc. 1. 

 no. 643. 1909. 



Plate IV. fig. 62. 



Plant mass thin, membranaceous, expanded, pale blue-green, golden 

 yellow or brick-colored; filaments flexuous, densely entangled; sheaths 

 narrow, papery, mucous or entirely diffluent into an amorphous mucus; 

 trichomes 1-1.5 mic. in diameter, not constricted at joints; apex of trichomc 

 straight, briefly tapering, not capitate; apical cell acute conical; calyptra 

 none; cells 2-4 mic. in length; transverse walls marked by four refringent 

 granules, usually inconspicuous; cell contents blue-green. 



Alaska. Forming a thin, membranaceous stratum on perpendicular 

 rocks moistened by spray from a waterfall. Orca, Prince William Sound. 

 (Saunders). Pennsylvania. Quiet waters. (WoUe). Nebraska. In run- 

 ning water in greenhouse. Lincoln. (Bessey). Wyoming. In overflow 

 water of spring where the old formation makes a hard, billowy or terraced 

 incline. The algae extend down the incline for a distance of twenty feet, 

 forming wide ribbons of green, alternating with bands of pink, yellow, 

 white and a darker green. Temperature of spring 91° C. Algal growth oc- 

 curs at a temperature of 51-55° C. Ribbon Spring, Norris Geyser Basin. 

 June i8g6; in small shallow spring, expanding at top into leaf-like masses, 

 or tapering from bulbous head to a small tubular base, temperature 55" C, 

 Valley of Nez Perces Creek, Lower Geyser Basin, June 1896; in grassy 

 rivulet, temperature 30° C, Mountain hot springs, Lower Geyser Basin, 

 June 1896; around edges of springs, forming brown and green layers which 

 turn gray or blackish out of water, temperature 63° C, Prismatic Lake, 

 Middle Geyser Basin, July 1896; forming plumy strings, white or light 

 yellowish in color, temperature 75.5° C, Solitary Spring, Upper Geyser 

 Basin, July 1896; forming a whitisih, scurfy, hardened, rather brittle scum 

 on surface of still pool into which overflow runs, temperature 41° C, 

 Mammoth Hot Springs, July 1896, Yellowstone National Park. (Tilden). 

 Washington. In a water trotfgh fed by a spring. San Juan Island. July 1901. 

 (Gardner). Central America. In a pool of very warm water close to a 

 hot spring. Near Lake Amatitlan. January 1906. (Kellerman). West 



Indies. Royal Botanical Gardens, St. Ann's, Trinidad. (Howard). 



This species was found to be "by far the most widespread and abun- 

 dant of any alga in the hot waters of the Park. Its habit of growth is 

 extremely varied, so that it is not easily recognized. It is the only species, 

 except Spirulina major, that, so far as I know, is found in both 

 calcareous and silicious waters in this region." — Tilden. 



Forma weedii Tilden. Observations on some West American Thermal 

 Algae. Bot. Gaz. 25: 99. pi. 9- f. 16. 1898. De Toni. Syll. Algar. 5: 226. 1907. 



Plant mass blue-green; filaments often strongly bent; sheaths not 

 visible, trichomes 2.5-3 mic- in diameter; apex of trichome sharply bent; 

 cells 1.5-2.5 mic. long; transverse walls generally distinct, sometimes 

 marked by granules; cell contents usually granular. 



Wyoming. In overflow of channel. Temperature 49-54-3°' C. With 

 Spirulina major. Spasmodic Geyser, Upper Geyser Basin, Yellow- 

 stone National Park. 1897. (Weed). 



