Myxophyceae 93 



B Trichomes not constricted at joints 



a Plants epiphytic, living in salt water; trichomes 4-4.5 mic. in 

 diameter, irregularly curved, very rarely straight; apex of 

 trichome gradually tapering; cells 4-11 mic. in length 



P. laysanense 

 b Plants living in warm or fresh water; trichomes 4.5-9 mic. in 

 diameter, elongate, flexuous; apex of trichome gradually ta- 

 pering; cells 3-7 mic. in length P. favosum 

 c Plants living in warm or fresh water; trichomes 6-8 mic. in 

 diameter, apex of trichome scarcely tapering; apical cell 

 oblique, depressed, conical P. talidum 

 d Plants living in fresh water; trichomes 5.5-11 mic. in diameter, 

 straight, fragile; apex of trichome briefly tapering; apical cell 

 straight, conical; cells 2-4 mic. in length 



P. subfuscum 

 (3) Apex of trichome more or less curved, capitate 

 A Plant mass blue^green or dark brown 



a Plants living in fresh water; trichomes 6-9 mic. in diameter; 

 apex of trichome curved or briefly spiraled 



P. uncinatum 



b Plants living on damp soil or on rocks, rarely under water; 

 trichomes 4-7 mic. in diameter; apex of trichome scarcely 

 curved, sometimes straig'ht P. autumnale 



B Plant mass dark purple P. setchellianum 



184. Phormidium fragile (Meneghini ) Gomont. Monogr. Oscill. 183. pi. 4. 

 f. 13-15. 1893. De Toni. Syll. Algar. 5: 220. 1907. 



Collins. Algae. Rand and Redfield's Flora of Mount Desert Island, 

 Maine. 248. 1894. Collins, Holden and Setchell. Phyc. Bor.-Am. Fasc. 

 ID. no. 451. 1898. Collins. Preliminary Lists of New England Plants. — V. 

 Marine Algae. Rhodora. 2: 42. 1900. West and West. A further Contri- 

 bution to the Freshwater Algae of the West Indies. Journ. Linn. Soc. Bot. 

 34: 289. 1898-1900. Bessey, Pound and Clements. Additions to the Re- 

 ported Flora of the State. Bot. Surv. Nebraska. 5: 13. 1901. 



Plate IV. fig. 52, 53. 



Plant mass mucous, lamellose, yellowish or dark blue-green; sheaths 

 gelatinous, fibrous, diffluent into mucous; trichomes 1.2-2.3 mic. in diame- 

 ter, more or less flexuous, entangled or somewhat parallel to each other, 

 constricted at joints; apex of trichome tapering; apical cell acute-conical; 

 calyptra none; cells 1.2-3 mic. long; cell contents not granular. 



Maine. Forming a dull green, gelatinous stratum on woodwork. Near 

 Seal Harbor; forming an encrustation in a tide pool, York Island, Penob- 

 scot Bay, July 1894. (Collins). Massachusetts. Northern part. (Collins). 

 Nebraska. In aquaria. Lincoln. (Bessey). West Indies. In stream. Wot- 

 ten Waven, Dominica. (Elliott). 



