124 CONTEIBUTIONS FROM THE NATIONAL HEKBAEIUM, 



40. Carex hystricina Muhl.; Willd. Sp. PI. 4: 282. 1805. 

 Type locality: "Habitat in humidis Pennsylvaniae." 

 Range: British America to Georgia, Nebraska, and New Mexico. 

 New Mexico: North Percha Creek {Metcalfe 1122). 



41. Carex rostrata Stokes in With. Bot. Arr. Veg. Brit. ed. 2. 2: 1059. 1787. 

 Type locality: "Bogs of Isla, and on Bentelkerny and Breadalbane," England. 

 Range: British America to California, New Mexico, and New York; also in Europe. 

 New Mexico: Truchas Peak; Silver Spring Canyon; Chama. Bogs, Transition to 



Arctic-Alpine Zone. 



9. KOBRESIA Willd. 



Slender tufted perennial with erect culms and solitary spikes; spikelets 1 or 

 2-flowered, spicate; perigynium none; stigmas 3; achenes obtusely 3-angled, sessile. 



1. Kobresia beUardi (All.) Degland in Loisel. Fl. Gall. 2: 626. 1807. 



Carex bellardi All. Fl. Pedem. 2: 264. pi. 92. f. 2. 1785. 



Kobresia scirpina Willd. Sp. PL 4: 205. 1805. 

 . Elyna spicata Schrad. Fl. Germ. 1: 155. 1806. 



Elyna bellardi Koch, Linnaea 21: 616. 1848. 



Type locality: European. 



Range: Arctic America, south in the Rocky Mountains to northern New Mexico; 

 also in Europe and Asia. 



New Mexico: Costilla Valley (TFboion). Wet ground. 



Order 11. ARALES. 

 15. LEMNACEAE. Duckweed Fafiiily. 

 Small unattached aquatics, the plant body a thallus, rooting from beneath. 



KEY TO the genera. 



Roots several from a prominently nerved thallus 1. Spirodela (p. 124). 



Root solitary from a faintly nerved thallus 2. Lemna (p. 142). 



1. SPIRODELA ScHLEiD. 



Thallus disk-shaped, 7 to 12-nerved, 2 to 10 mm. long, bearing a single cluster of 

 4 to 16 elongated roots; spathe sacUke; ovary 2-ovuled; fruit unknown. 



1. Spirodela polyrhiza (L.) Schleid. Linnaea 13: 392. 1839. 

 Lemna polyrhiza L. Sp. PI. 970. 1753. 

 Type locality: "Habitat in Europae paludibus fossis." 



Range: In still water throughout most of North America and in the Old World. 

 Reported by Mr. J. R. W'atson from "ponds about the fair grounds, Albuquerque." * 



2. LEMNA L. Duckweed. 



Thallus disk-shaped, usually provided with a central nerve, with or without lateral 

 ones, each with a single root; ovary with 1 to 6 ovules; fruit ovoid, more or less ribbed. 



KEY TO THE SPECIES. 



Fronds long-stipitate, narrowly oblong, 6 to 10 mm. long, mostly sub- 

 merged, often forming large masses. 1. L. trisulca. 



Fronds not stipitate, broadly elliptic to obovate, 3 mm. long or less, 

 floating. 



Fronds obovate, 3 mm. long; fruit more or less lenticular 2. L. minor. 



Fronds elliptic or oblong, 2 mm. long or less; fruit elongated 3. L. minima. 



1 Bull. Univ. N. Mex. 49: 94. 1908. 



