Nitella opaca C. A. Agardh 1824, p. 124 

 PL 79, Figs. 4-10 



Plants large and robust with very long internodes (2-4 times 

 longer than the branchlets); nodes bearing 6-7 branchlets which 

 may be either simple or once-divided, ultimate rays 1-celled and 

 mucronate; fertile branchlets crowded, forming heads; sex organs 

 dioecious, the oogonia 1-2, broadly ovoid, 0.5-0.565 mm. in diameter, 

 0.6.5-0.7 mm. long, the investing cells showing 7-9 turns, the crown 

 0.25-0.4 mm. high, deciduous; antheridia 0.65-0.75 mm. in diameter. 



Common; a very luxuriantly growing, bushy plant, often forming 

 dense beds, especially in soft water lakes; sometimes found at a 

 depth of 5-8 meters. Mich., Wis. 



Nitella tenuissima ( Desv. ) Kuetzing 1843, p. 319 

 PI. 80, Figs. 1-7 



Plants small, tufted, 2-8 cm. high, with several branches arising 

 from a single basal node; stem very slender, bearing whorls of 6 

 branchlets which are short, densely crowded and form glomerules, 

 giving a distinct beaded appearance to the plant; the branchlets 

 forking 3-4 times, ending in 2-celled rays; sex organs monoecious, 

 the oogonia spherical or broadly elliptic, about 260/i, ( 0.26 mm. ) in 

 diameter, 400/i, (0.4 mm.) long, invested by corticating cells that 

 show 9 turns; antheridia about 0.175 mm. in diameter. 



Like N. Batrachosperma, this species is often overlooked because 

 it grows in silt, with only the tips of the branches emergent. 



Growing in shallow water on silty bottoms, mostly in soft water 

 or slightly acid lakes. Mich., Wis. 



TOLYPELLA (A. Braun) Leonhardi 1863, p. 72 

 Thallus relatively coarse, (8)-10-25 cm. high, light green or gray- 

 green in color, usually irregularly branched, presenting a scraggly 

 appearance; sterile branches 6-16 in a verticil, of variable length; 

 fertile branches involving several long, and one head of short, 

 branchlets; internodes of principal filament and of primary laterals 

 long; uncorticated; primary laterals sparsely branched; branches 

 terminating in a series of unbranched ray cells which may be pointed 

 or bluntly rounded at the tip; monoecious (in our specimens), the 

 antheridia sessile or at the ends of short lateral branchlets in the 

 furcations; oogonia usually crowded, appearing to be above and 

 also beside the antheridia on the same node, formed either at the 

 base of a fertile branchlet or on one of the lower nodes, the coronula 

 persistent or not; oospore round in cross section, light to orange- 

 brown in color. 



[ 333] 



