DIANDRIA MONOGYNIA 9 



Stem SO to 40 feet high ; young branches and petioles covered with a velvety pu- 

 bescence. Leaflets lanceolate, narrower than the preceding, on shorter petioles, 

 and more pubescent beneath. Samara terete and tapering below, almost acute at 

 base, with a long narrow linear-lanceolate wing. 

 Hab % Low grounds; Brandywine, Sec. common. Fl. May. Fr. 



Obs. This is generally a smaller tree than the preceding ; but is scarcely dis- 

 tinguished from it by careless observers,— being commonly called by the same 

 name, and used for the same purposes. I entirely overlooked it, when my Cata- 

 logue was prepared. 



9. LEMNA.Z,. J\'utt. Gen. 28. 

 [Greek, Lemma, bark, husk, or scale ; from the form of the fronds.] 



Sub-monoicous : Calyx monosepalous, membranaceous, urceolate. 

 Corolla 0. Stamens 2 (rarely wanting), collateral. Ovary round- 

 ish, flat above, keeled beneath ; style as long as the ovary : stigma flat. 

 Fruit a utricle; seed 1, oval, lying horizontally, fixed by its lower 

 surface. Hooker. 



Minute herbaccous.Jfoatin" plants ; f >rming a series of lenticular fronds, with 

 one or moro roots from the centre, beneath,— and producing flowers, and young 

 fronds, from their cleft margins. K<it . Ord. 260. Lindl. PlSTlACBJB. 



1. L. trisulca, L. Fronds thin, elliptic-lanceolate, caudate at base, 

 serrate at apex ; root solitary. Heck, Hot. p. 383. 

 Three-furrow, or three-lored Lemna. 



Root a single fibre, terminated at the extremity by a sheath-like appendage, re- 

 sembling the calyptra of mosses. Fronds one-third to three-fourths of an inch 

 long, membranaceous, nearly pellucid, attenuated at base into a slender tail or 

 petiole,— obtuse at apex, and erose or somewhat serrate ; producing flowers, or a 

 young frond, on each side, from a longitudinal cleft in the margin, near the middle. 

 While these lateral fronds remain sessile, they present the appearance of a three 

 lobed leaf. 



Ilab. Stagnant waters: New Garden township: rare. Fl. Fr. 



Obs. All the species are believed to be annual. This one was found by Mr. 

 Joshua Hoopes, September, 1833, near Phillip's Lime quarries, New Garden. 



2. L. minor,/,. Fronds nearly oval, sessile; root solitary. Heck, 

 Hot. p. 383. 



Lesser Lemxa. Vxdgo— Duck's Meat. Duckweed. 



Root a solitary fibre. Fronds minute, about a line, or a line and a half long, 

 roundish ovate or oval, somewhat succulent, sessile, with a cleft in the margins 

 near the base, producing flowers and young fronds. 

 Hab. Ponds of still water: common. Fl. Fr. 



Obs. This species is often very abundant in stagnant waters, so as to furnish a 

 verdant covering to lanre portion! of their surface. It is said that Ducks feed on 

 it: hence its common name. 



3. L. polyrhiza, L. Fronds roundish-obovatc ; roots numerous, 

 fascicled. Heck, Hot. p. 383. 

 Mant-hooted Lkmxa. 



Root a fascicle of fibres from near the centre of the frond. Frauds from 2 to 4 

 lines Ion-, sessile, of a firmer texture than either of the preceding distinctly nerv- 

 ed above, and often dark purple beneath. 



Hub. Stagnant pools: Black rock, .Schuylkill: not common. Fl. Fr. 



