Myxophyceae 211 



Collins. Preliminary Lists of New England Plants. — V. Marine Algae. Rho- 

 dora. 2: 42. 1900. 



Plate XI. fig. 10. 



In a crust formed by various blue-green algae; filaments scarcely 

 elongate, entangled in dense balls, radial because of pressure, strongly 

 tortuous, tapering at the apices, branched; false branches in pairs, spread- 

 ing, often parallel; sheaths thick and orange brown in the middle portion 

 of the filament, gradually becoming thinner and faded at the ends; trich- 

 omes 2-2.5 m'c. in diameter, constricted at joints; apical cell rotund; cells 

 shorter than their diameter, cell contents pale blue-green. 



Massachusetts. Marblehead. January 1889; with other algae, on rocks 

 near high water mark, Nahant, June 1889. (Collins). 



389. Plectonema battersii Gomont. Sur quelques Oscillariees Nouvelles. 

 Bull. Soc. Bot. de France. 46: 36. 1899. De Toni. Syll. Algar. 5: 

 495. 1907. 



Collins. An Algologist's Vacation in Eastern Maine. Rhodora. 4: 177. 

 1902; Notes on Algae. — VI. Rhodora. 5: 233. 1903. Collins, Holden and 

 Setchell. Phyc. Bor.-Am. Fasc. 22. no. 1060. 1903. 



Plant mass blackish or brownish green; filaments elongate, flexuous, 

 abundantly and repeatedly branched; false branches usually in pairs, more 

 slender than the main filaments; sheaths colorless, somewhat thick in the 

 main filaments; trichomes 2-3.5 ™'c. in diameter, constricted at joints, with 

 somewhat tapering apices; apical cell rotund; cells shorter than their 

 diameter; cell contents homogeneous, pale blue-green. 



Maine. In a runway on rocks from upper pools. Brownie Island, Jones- 

 port. July 1902; Harpswell. (Collins). Massachusetts. Marblehead Neck. 

 August 1902. (Collins). 



Genus SCYTONEMA Agardh. Syst. Algar. 26. 1824. 



Filaments branched; false branches usually arising between two hetero- 

 cysts, solitary or in pairs, formed by the lateral perforation of the sheath 

 by the trichome; trichomes single within the sheath, straight; hormogones 

 terminal, solitary; gonidia spherical or oval, observed in a few species; 

 wall of gonidium thin, smooth. 

 I Sheaths homogeneous or formed of parallel layers. 



1 Plants living in fresh water 



(i) Filaments 5-8 mic. in diameter S. conchophilum 



(2) Filaments 12-16 mic. in diameter S. arcangelii 



(3) Filaments 18-24 mic. in diameter S. coactile 



(4) Filaments about 30 mic. in diameter S. rivulare 



(5) Filaments 36 mic. in diameter S. occidentale 



(6) Filaments 16-36 mic. in diameter S. crispum 



2 Plants living in warm water 



(i) Filaments 16 mic. in diameter S. caldarium 



