74 XYRIDACEAE 



2. Lemna minor L. Lesser Duckweed. (Man. p. 233; I. F. f. 

 SS8.) In ponds, lakes and stagnant waters throughout N. Am. Also in 

 Eu., Asia, Africa and Australia. — Pcriftsy/vania : Northampton ; Dela- 

 ware ; Lancaster ; Dauphin ; Huntingdon ; Philadelphia ; 

 Chester. 



3. Lemna perpusilla Terr. Minute Duckweed. (Man. p. 233; I. 

 F.y. SSy.) In ponds, rivers, springs, N. Y. and N. J. to Minn., Neb. 

 and Mo. — Petuisylvania : Northampton. 



3. SPIRODELA Schleid. 



1. Spirodela polyrhiza (L. ) Schleid. Greater Duckweed. (Man. 

 p. 232 ; I. F. y". 884.) In rivers, ponds, and shallow lakes, N. S. to B. C, 

 S. C, Mex. and Nev. In the Old World and in tropical Am. — Pennsyl- 

 vania : Philadelphia ; Northampton ; York ; Dauphin ; Hunting- 

 don ; Bucks ; Lancaster ; Chester ; Delaware. 



Order 7. XYRIDALES. 



Ovary i-celled, with parietal placentae : inflorescence without a spathe. 



Fam. I. XYRIDACEAE. 



Ovary 2-3-celled, if inconipletelj' so or if nearl}- i-celled then the flowers in a 

 spathe. 

 Flowers minute, monoecious or dioecious, in dense heads each seated in an 



imbricated involucre. Fam. 2. Eriocaulace.\e. 



Flowers conspicuous or relatively so, perfect. 

 Calyx and corolla free, of very diff'erent members : stamens free. 



Fam. 3. COMMELINACEAE. 



Calyx and corolla of quite similar members and partially united : stamens 

 partially adnate to the perianth. Fam. 4. Pontederiaceae. 



Family i. XYRIDACEAE Lindl. Yellow-eyed Gr.ass Family. 



1. XYRIS. 



Lateral sepals wingless, the keel fringed with short hairs, i. X.flexuosa. 

 Lateral sepals winged, the keel fimbriate or lacerate. 



Heads oblong, 3-6 mm. long. 2. X. montana. 



Heads ovoid or oval, 8-16 mm. long. 3. X. Caroli7iiana. 



1. Xyris flexuosa Muhl. Slender Yellow-eyed Grass. (Man. 

 p. 235 ; I. F.y. 8gs. ) In wet places, Me. to Minn., Ga. and Tex. — Penn- 

 sylvania : Montgomery; Delaware ; Berks ; Lancaster. 



2. Xyris montana H. Ries. Northern Y'ellow-eyed Grass. 

 (Man. p. 235 ; I. F./. c?p^.) In bogs, N. S. to Mich., and in the moun- 

 tains of Pa. and '^.'^.—Pennsylvania : Monroe ; Lackawanna. 



3. Xyris Caroliniana Walt. Carolina Yellow-eyed Grass. ( Man. 

 p. 236 ; l.V.f. 8g6,) In wet places, Mass. to Fla. and La., mostly near 

 the coast. — Pennsylvania: Monroe; Delaware; L-ancaster ; Y'ork ; 

 Carbon ; Chester. 



