54 University of California ruhlications in Botany [Vol.8 



Stizeubergor, Spiruli}ui und Arthospira, in Hedwigia, vol. 1, 

 1852, p. 32. 



Tlie type species is Arthrospira Jenncri (Hass.) Stizenb., a fresh 

 water plant from Tunbridge. Arthrospira is intermediate between 

 Oscilhtoriu and Spirnlina. Some species of Oscillatoria, sucli as 0. 

 Bonnemai-so'iiii Crouan are loosely, but regularly, spiral. The coarser 

 species of Arthrospira approach these. On the other hand, the looser 

 and laxer species of Arthrospira, e.g., Arthrospira niiniata (Hauck) 

 Gomont which is slender and with the dissepiments obscure, approach 

 Spirulin-a. In certain slender but straight species of Oscillatoria, e.g., 



0. amphihiu Ag., the dissepiments are as obscure as in species of 

 Spirulina until they are revealed by treatment with strong solutions 

 of chromic acid (cf. Gomont, 1893, pi. 7, figs. 4, 5). In the same 

 fashion, treatment with chromic acid reveals the dissepiments in 

 species of Spirulina (cf. also Gardner, 1917, p. 377). 



Key to the Species. 



1. Cells 7-9/A in diam., 5-7/a long 1. A. maxima (p 54) 



1. Cells 14.5-16/A in diam., 2.5-3.5/a long 2. A. breviarticulata (p 5.5) 



1. Arthrospira maxima S. and G. 

 Plate 8, fig. 3 



Trichomes 7-9/^, diam., forming an open regular spiral of 3-8 turns, 

 40-60|U diam., 70-80/a between the turns, slightly tapering at the ends ; 

 cells 5-7fjL long, not constricted, with numerous, coarae, angular, 

 refringent granules frequently crowded at the partitions; end walls 

 of terminal cells rounded, slightly thickened; color verdigris green. 



Found floating among other species of Myxophyceae in a warm 

 salt-water pond. Known only from a single locality, viz., in a hot, 

 salt-water pond. Key Route pool, in Oakland, California, on the shore 

 of San Francisco Bay. 



Setchell and Gardner, in Gardner, New Pac. Coast Alg. I, 1917, 

 p. 377, pi. 33, fig. 3 ; Collins, Holden and Setchell, Phyc. Bor.-Amer. 

 (Exsicc), no. 2259. 



The salt water of this pond was pumped from the bay and used 

 for condensing the steam of a power house, the same water being 

 used repeated!}^, thus it became alternately heated and cooled. This 

 treatment subjected the floating algae to the unusual condition of 

 extremes of heat and cold under which it thrived abundantly. 



