2O 



ules (though, being immature, the character of the "Nordstedt mark- 

 ings " is somewhat doubtful). 



These plants exhibit a marked tendency to the " congestae " section, 

 though in but few of the plants are found decided condensations of the 

 fruiting leaves. 



This species was collected for the United States National Herbarium 

 by J. B. Leiberg on June 30, 1894, in ''shallow pools which dry up in 

 middle summer, under and among the submerged Artemisia shrubs, 

 near Button Springs, Lake Co., eastern Oregon. Alt. 1470 meters." 



Explanation of Plate. Fig. I, plant, natural size; Fig. 2, a verticil and leaf 

 X 25 ; Fig. 3, a spore X 5 > Fig. 4, surface of spore, highly magnified. 



N. MUCRONATA. A. Br. (N. flabellata Kg. ; N. exilis A. Br.). 



Plants about medium size, strong and erect, freely branched, almost 

 bushy in habit; color dark green, or even brownish; stems, numerous 

 from a single root, 0.8 to i mm. in diam. Leaves six in a verticil, 

 twice or, when fertile, thrice divided ; terminal segments two (rarely 

 three) celled, the ultimate cell consisting of a slender mucro. This ter- 

 minal mucro is much smaller (three to eight times) than the preceding 

 cell. In fruiting the plant is monoecious, and the fruit is not enveloped 

 in mucus. The oogonia are usually single, rarely aggregated ; the 

 oospore (nucleus) is dark-brown or nearly black, with seven rather 

 prominent and sharp ridges (spirals), 260 to 360 long; its surface is 

 reticulated. 



This plant has been found occasionally in this country, but it seems 

 to be much more common in Europe. It is quite variable ; in its 

 slender and more delicate forms, approaching N. gracilis Ag., A. 

 Braun distinguished three sub-species found in America, var. tenuior 

 {N. flabellata Kuetz, N. exilis A. Br.), a slender form with isolated 

 oogonia, with prominent striae on the nucleus, Cambridge, Mass., and 

 Texas. Var. virgata, " robustior, longi-furrata," oospores aggregated, 

 Merrimac River, N. H., "in Herb. Decaisne, coll. by Green" (JV. 

 virgata Wallm.): var. pachygyra from North Carolina and Texas. In 

 Herb. Engelmann is the following note by A. Braun: "I considered 

 this formerly as Ch. Elliotti (same as Ch. capitata Ell.), but find now 

 that it is somewhat different from the Schweinitz specimen from Caro- 

 lina, and Le Conte's from Georgia; it cannot be distinguished from the 

 European Ch. flabellata A. Br. 



Another specimen, "A 7 . Braunfels Tex., collected by C. Wright, 

 1850, and also running water of the Leona," is labelled N. flabellata 

 Kuetz, Ch. exilis A. Br., and subsequently re-named N. oligospira var. 

 Wrightii A. Br. "near N. mucrona-temiior or flabellata" A speci- 



