STATE GEOLOGIST. 137 



P. lUinoensis, Morong.* Pondweed. 



Emmet county, Iowa, Cratty, Arthur; doubtless also to be found in southern Min- 

 nesota. 



P. perfoliatiis, L. Pondweed. 



Throughout the state. Blue Earth county, Leiberg; lake Calhoun, Minneapolis, 

 Upham-^ Stearns county, Camn'bell; lake of the "Woods, Dawson. 



P. perfoliatiis, L., var. lanceolatus, Robbins. Pondweed. 



Also throughout the state. Lake Minnetonka, ArtMir; frequent in Martin county, 

 and in Emmet county, Iowa, Grotty. 



P. zosteraefoliiis, Sclium. (P. compressus, Fries, not L.) Pondweed. 



Minneapolis, Simmons; Blue Earth county, Leiberg, and Martin county (frequent), 

 Cratty, both determined by Rev. T. Morong. 



P. paiiciflorus, Parsh. Pondweed. 



Minneapolis (common). Miss Butler; lake Pepin, Miss Manning; Blue Earth county, 

 Leiberg, determined by Rev. T. Morong; Emmet county, Iowa (frequent), Cratty. 

 [North of lake Superior, Agassiz.} 



P . pusillus, L. Pondweed. 



Throughout the state. Lake of the Woods, Dawson; White Bear lake, Ramsey 

 county, Simmons; Emmet county, Iowa, Cratty, determined by Rev. T. Morong. 



P. pusillus, L., var. major, Fries. Pondweed. 



Martin county (frequent), Cratty, determined by Rev. T. Morong. 



P, pusillus, L., var. vulg-aris, Fries. Pondweed. 



Lake Minnetonka (plentiful), HerricU, Roberts; Wiuona lake, Holzinger. 



P. pectinatus, L. Pondweed. 



Throughout the state. Mississippi river near Saint Cloud, Campbell; Blue Earth 

 county, Leiberg; Martin county (abundant), Cratty, determined by Rev. T. Morong. 

 [North of lake Superior, Agassiz; James river, Dakota, Geyer.] 



ALISMACEiE. Watee-Plantain Family. 



TRIGIiOCHIN, L. Arkow-grass. (This genus and Scheuch- 

 ZERIA are included in the preceding order, Naiadace^, by Watsonin the Botany 

 of California.) 



*POTAMOGETO]sr iLLiNOENSis, Moroug. Stem stout, branching towards the sum- 

 mit ; floating leaves opposite , thick, coriaceous, oval or ovate, 2 to 3 inches long by li4 

 broad, 19- to 23-nerved, rounded or sub-cordate at base, and with a short blunt point at 

 the apex, on short petioles ; submersed leaves comparatively few, dark green, oblong- 

 elliptical, acute at each end, usually ample (the largest nearly 8 inches long and 514 

 wide), entire, rarely mucronate, nearly or quite sessile, the uppermost opposite; stipules 

 coarse, free, obtuse, strongly bicarinate, about 2 inches in length ; peduncles often 

 clustered at the summit of the stem, 2 to 4 inches long, usually somewhat thickening 

 upwards ; spikes about 2 inches long, densely flowered ; fruit roundish obovate, IM 

 to 2 lines long and 1 to 114 lines wide, 3-keeled on the back, the middle keel prominent 

 and sometimes shouldered at the top, flattened and slightly impressed on the sides, 

 obtuse or occasionally pointed at the base, the style short and nearly facial, the apex of 

 the embryo pointing transversely inwards. Allied to P. lucens, L., in habit, but with 

 larger fruit, and in foliage quite distinct. Morong in Botanical Gazette, vol. v, p. 50 

 (May, 1880). 



