74 XYRIDACEAB 



2. Lemna minor L. LESSER Duckweed. (Man. p. 233 ; I. F. / 

 888.) la ponds, lakes and stagnant waters throughout N. Am. Also in 

 Eu., Asia, Africa and Australia. — Pennsylvania : Northampton ; Dei,a- 

 wARS ; Lancaster ; Dauphin ; Huntingdon ; Phii,adei,phia ; 

 Chester. 



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

 F./. 887.) In ponds, rivers, springs, N. Y. and N. J. to Minn., Neb. 

 and Mo. — Pennsylvania Northampton. 



3. SFIRODELA Schleid. 



1. Spirodelapolyrhiza(L.) Schleid. GREATER Duckweed. (Man. 

 p. 232 ; I. F./. 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 : Phii,adei,phia ; 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 incompletely so or if nearly i-celled then the flowers in a 

 spathe. 

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



imbricated involucre. Fam. 2. Eriocaulaceae. 



Flowers conspicuous or relatively so, perfect. 

 Calyx and corolla free, of very different members : stamens free. 



Fam. 3. Commblinaceae. 



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 Grass Family. 



1. XYRIS. 



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

 Lateral sepals winged, the keel fimbriate or lacerate. 



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



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



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

 p. 235 ; I. F./. ,?pj. ) In wet places, Me. to Minn., Ga. and Tex. — Penn- 

 sylvania : Montgomery ; Delaware ; Berks ; Lancaster. 



2. Xyris montana H. Ries. Northern Yellow-eyed Grass. 

 (Man. p. 235 ; I. F./. 894.) In bogs, N. S. to Mich., and in the moun- 

 tains of Pa. and T^.'^.— Pennsylvania : Monroe ; Lackawanna. 



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

 p. 236 ; I. v./. 8g6.) In wet places, Mass. to Fla. and La., mostly near 

 the coast. — Pennsylvania : Monroe ; Delaware ; Lancaster ; York ; 

 Carbon ; Chester. 



