Myxophyceae 85 



omes 7-16 mic. in diameter, not constricted at joints, those in center of 

 colony having the form of twisted ropes, free at the ends; apex of trich- 

 oma briefly tapering or sometimes inflated; cells 8-26 mic. in length, rarely 

 somewhat quadrate; transverse walls often granulated; cell contents coarse- 

 ly granular. 



West Indies. Guadeloupe. (Thiebaut). In plankton. (Murray and Black- 

 man. Hawaii. In plankton between the islands of Hawaii and Laysan. 

 1896-1897. (Schauinsland). 



172. Trichodesmium contortum Wille in Brandt. Nordisches Plankton. 



Lief. 2. Abt. 20. 18. f. 14. De Toni. Syll. Algar. 5: 204. 1907. 

 Lemmermann. Algenfl. Sandwich-Inseln. Bot. Jahrb. 34: 618. 1905. 



Plate IV. fig. 43. 



Colonies spirally twisted, light yellow; trichomes 16-25 mic. in diame- 

 ter, twisted together into cords; cells somewhat quadrate; cell contents 

 uniformly granular. 



Hawaii. In plankton between the Islands of Hawaii and Laysan. 1896- 

 1897. (Schauinsland). 



Genus ARTHROSPIRA Stizenberger. Hedwigia. i: 32. 1852. 



Trichomes multicellular, cylindrical, without a sheath, forming a very 

 regular, more or less loose spiral; apex of trichome sometimes tapering; 

 apical cell rotund; calyptra none. 



I Trichomes 5-8 mic. in diameter, forming a loose spiral 9-1S mic. in 



diameter, the distance between the turns being 21-31 mic. 



A. jenneri 



II Trichomes 2.5-3 mic. in diameter, forming a rather loose spiral about 



6 mic. in diameter, the distance between the turns being 16-18 mic. 



A. gomontiana 



173. Arthrospira jenneri (Kuetzing) Stizenberger. Spirulina and Arthro- 



spira. Hedwigia. i : 32. 1852. Gomont. Monogr. Oscill. 267. pi. 7. f. 



26. 1893. De Toni. Syll. Algar. 5: 206. 1907. 

 WoUe. Fresh-Water Algae U. S. 323. pi. 210. f. 2. 1887. (Spirulina 

 jenneri Kuetz.) Bennett. Plants of Rhode Island. 115. 1888. Til- 

 den. List of fresh-water Algae collected in Minnesota during 1893. Minn. 

 Bot. Studies, i: 31. 1694. Saunders. Protophyta-Phycophyta. Flora of 

 Nebraska. 23. pi. i. f. 7. 1894. Riddle. Algae from Sandusky Bay. Ohio 

 Nat. 3: 317. 1902. Brown. Algal periodicity in certain ponds and streams. 

 Bull. Torr. Bot. Club. 35: 248. 1908. 



Plate IV. fig. 44- 



Plant mass thin; trichomes 5-8 mic. in diameter, often growing among 

 other algae, fragile, forming a loose spiral 9-15 mic. in diameter, sometimes 

 slightly constricted at joints; apex of trichome not tapering, nor capitate; 

 cells quadrate or shorter than the diameter, 4-5 mic. long; transverse walls 

 sometimes finely granulated; cell contents scarcely granular, dark blue- 

 green. 



