2. Whorls of verticils at the nodes globular in outline, gradually 

 decreasing in size toward the apex of the main 

 axis, forming minute tufts at the tip N. tenuissima 



2. Whorls of verticils at the nodes spreading, not forming compact 

 globules, becoming compactly arranged at tlie anterior end and 



forming dense clusters cone-shaped in outhne — N. Batrachospertna 



3. Plants monoecious N. jiexilis 



3. Plants dioecious N. opaca 



Nitella Batrachosperma ( Reichenb. ) A. Braun 1847, p. 10 



PL 78, Figs. 1-4 



Plants minute and very delicate, up to 2 cm. (rarely 3 cm.) tall, 

 with several branches arising from a basal node; internodal cells in 

 the lower part of the thallus 2-3 times the length of the verticils, 

 which are in whorls of 8 at the node, and spreading, the branchlets 

 crowded toward the apex, forming a cone-shaped cluster at the tip; 

 branchlets once or twice divided, the ultimate rays 2-celled, the 

 terminal cell awl-shaped; monoecious; antheridia terminal on a 

 short stalk in the furcation of a 'leaf,' 0.135-0.210 mm. in diameter; 

 oogonia borne laterally to the antheridia and below them, with a 

 persistent coronula; oospore globose, 0.27-0.30 mm. in diameter, 

 dark brown in color, the outer membrane with reticulations. 



This species is the smallest and the most delicate one in our 

 collections. Like N. tenuissima, it has a gray-green color, is often 

 found embedded in silt in the bottoms of shallow ponds and lagoons 

 and hence is easily overlooked. 



Mich. 



Nitella flexilis (L.; C. A. Agardh 1824, p. 124 

 PI. 79, Figs. 1-3 



Plants large (up to 30 cm. tall) and stout, with long internodes 

 (about 2 times longer than the branchlets), repeatedly branched, 

 especially long and sprawling stems in deep water; nodes bearing 

 whorls of 6-8 branchlets, with the sex-organ-bearing branchlets 

 usually shorter, forming dense clusters, the branchlets but httle 

 divided, usually only one, the ultimate rays 1-celled and ordinarily 

 acuminate; sex organs monoecious, the oogonia 2-3, subglobose or 

 broadly ovoid, 0.55-0.75 mm. in diameter, 0.B25-0.9 mm. long, 

 the investing cells showing 8-9 turns; antheridium 0.5-0.75 mm. in 

 diameter. 



In shallow water of soft water lakes and Sphagnum bogs; from 

 10-12 meters. Mich., Wis. 



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