BLUE-GREEN ALGAE 109 



38 (37) Filaments forming erect tufts, often branched. . Symploca Kiitzing. 



Filaments densely interwoven to form a slimy substratum from 

 which arise erect tufts of variable height. Sometimes more or less 

 procumbent. False branches solitary; sheaths thin, colorless, firm 

 or somewhat mucous; apex of the filament straight, sometimes a little 

 tapering; outer membrane of tlie apical cell slightly thickened in 

 some species. In hot springs, on damp earth, walls, or trunks of trees. 



Fig. 48. 



Symploca lucifuga Harvey, a, X 250; b, natural size. (After 

 Wolle.) 





39 (29) Several filaments in a common sheath which is frequently 



branched Subfamily Vaginareeae . . 40 



40 (41, 42) Sheaths often colored; lamellose; filaments few or many, loosely 



aggregated within the common sheath, Schlzothrix Kiitzing. 



Several filaments enclosed in a firm 

 lameUose sheath which is at first 

 colorless but later becomes yellowish, 

 brownish, or purpUsh; filaments simple 

 or variously branched. Forming cush- 

 ion-hke masses, erect tufts, or a flat 

 stratum on moist substrata, rarely 

 free-floating. 



Fig. 49. Schizothrix rubella NSgeli. 

 X 430. (After Gomont.) 



41 (40, 42) Sheaths hyahne, fused with adjoining sheaths. Hydrocokiim 



Kiitzing. 



Filaments composed each of 

 numberless short cells, the end 

 cell with thickened cap-like 

 membrane. Filaments two 

 to many in colorless, slimy 

 sheaths, which become fused 

 with those of adjoining fila- 

 ments. In brooks and water- 

 faUs. 



Fig. 50. Hydrocoleum homoeotrich- 

 um Kiitzing. X 390. (After 

 Gomont.) 



42 (40, 41) Sheaths hyaline, not lamellose, containing a large number of 



filaments Microcoleus Desmazieres. 



Filaments simple, consisting 

 generally of long cells; closcJy 

 aggregated in great numbers 

 in the center of a conspicuous, 

 hyaline, cyhndrical sheath. 



Fig. 51. Microcoleus dclicatulm 

 W. and G. S. West. X 35°- 

 (After West.) 



