long. Gonidia oblong or ovate; formed in a series and becoming 

 loosely arranged; 6-7 fi in diameter, 8-lOju, long. 



Growing on damp soil in marshy places; near margins of lakes. 

 Mich., Wis. 



Nostoc verrucosum Vaucher 1803, p. 225 

 PI. 121, Figs. 11-13 



A globular or buUate, verrucose and warty, leathery mass, many 

 colonies sometimes coalescing to form a large oHve-green or brown, 

 somewhat membranous expansion on soil or on submerged sub- 

 strates, solid at first but becoming hollow. Trichomes densely en- 

 tangled, especially in the outer firm layers of the colonial mucilage, 

 less compact inward; straight and radiating, frequently with indi- 

 vidual sheaths distinct. Gells compressed-spherical or disc-shaped, 

 3-4/x, in diameter, 2.5-4/i. long. Heterocysts spherical, 6/* in diameter. 

 Gonidia ovate, 5/a wide, 7/x long. 



Growing in 27-35 feet of water in semi-hard water lakes; some- 

 times large colonies are found floating or washed onto beaches of 

 lakes; also reported growing on rocks near a waterfall. Mich., Wis. 



WOLLEA Bornet & Flahault 1888, p. 223 



An attached tubular, saccate-cylindric, gelatinous colony of macro- 

 scopic size in which unbranched, simple trichomes of ovate or 

 cylindrical cells lie parallel, their sheaths confluent with the soft 

 colonial mucilage; heterocysts intercalary, or terminal through vege- 

 tative fragmentation of the trichome; gonidia ovate, solitary or in 

 a series, either adjoining the heterocyst or distantly removed from it. 



Wollea saccata ( Wolle) Bornet & Flahault 1888, p. 223 



PI. 122, Figs. 1, 2 



Characteristics as described for the genus. Plant mass irregularly 

 tubular or bullate, closed at the top, at first attached (usually in 

 shallow water ) , later expanding and forming soft, gelatinous masses 

 floating at the surface. Trichomes compactly arranged, mostly paral- 

 lel with the long axis of the colony, not contorted and twisted but 

 commonly curved. Cells ovate to subcylindric; constricted at the 

 cross walls; varying in their diameter throughout the length of the 

 trichome; 3.6-4.2-(5)/x in diameter, 5-10/^ long. Heterocysts ovate 

 to subcylindric; solitary; terminal or intercalary; 4-5ju, in diameter, 

 6.5-9/A long. Gonidia oblong or subcylindrical, with thin, smooth 

 walls; usually in a series of 3-5, rarely solitary; either near the hetero- 

 cysts or distant from them. 



This plant, although rare, has wide distribution in the United 



[526] 



