ALISMACK.t:. (WATKK-rLA:;TAlN FAMILY.) 553 



pons, ovate or oval, ohtuse, iritli srar-reli/ apiciilate operculum. — X. V. and N. J., 

 west to Mich, and Wise. — Var. TRiNfeuvis, Austin, lia.s larger, distinctly 3- 

 aerved fronds, and aii une(iually cordate seed. 



4. L. minor, L. Frauds round- to elllptic-ohocate (1-2^" in diameter), 

 rather tliiek, it/// obscure! i/ S-tierved ; apallie sac-like; utricle short-urn-sha|»ed, 

 tipped with a short style ; seed oblong-ohovate, amphiiropous, uitk promiutnt 

 rounded operculum. — [Stagnant waters, throughout N. Am. (Eu.) 



* * Ovules 2-7, auatropous ; fronds verj/ thick and spowj y , Jlat above, i:ery 

 obscurely b-nerved (1^-3" lony). 



5. Ij. gibba, L. Fronds ohovate-elliptic to nearly orbicular, almost hemi- 

 spherical, soon separating; bract sac-like. — Mo. (?) to Ariz, and Calif. 



3. WdLFFIA, Ilorkel. 



Flowers central, bursting through tlie upper surface of the globular (or in 

 some foreign ones flat) and loosely cellular frond, only 2 ; one consisting of a 

 single stamen with a 1-celled 2-valved anther; the other of a globular ovary, 

 tipped with a very short style and a depressed stigma. Ovule orthotropous, 

 rather oblique in the cell. Utricle spherical. Albumen thin. — Fronds root- 

 less, proliferous from a cleft or funnel-shaped opening at the base, the offspring 

 soon detached ; no rhaphides. — The simplest and smallest of flowering plants, 

 from i-f" long (an African and Cuban species much larger), floating as little 

 grains on the water. (Named for John Fred. Wo'ff, who wrote on Lemna in 

 1801.) 



1. W. Columbiana, Karsten. Globose or globular, \-%" long, very 

 loosely cellular, light green all over, not dotted; stomata 1-6; the opening 

 at the base circular and with a thin border. — Floating rather beneath the sur- 

 face of stagnant waters, Conn, to N. J., west to Minn, and La. 



2. W. Brasiliensis, Weddell. oblong, smaller and more densely cellu- 

 lar, flattish and deep green with many stomata above, tumid and pale below, 

 brown-dotted all over, anterior edge sharp, opening at base circular. — Growing 

 with the hist, but floating on the surface. 



Order 125. ALISMACE^. (Water-Plantaix Family.) 



Marsh herbs, with scape-like stems, sheath in (j leaves, and perfect or monoe- 

 cious or dicecious Jlowers ; perianth of Z herbaceous persistent sepals and 

 as many (often conspicuous) white deciduous petals, which are imbricate or 

 involute in burl; sfnrnens G or more, included; ovaries numerous, distinct ^ 

 1-celled and mostly l-ovuled, becoming achenes in fruit (in our genera) ; 

 seeds erect ; campylotropous. — Roots fibrous ; leaves radical, potiolate and 

 strongly nerved with transverse veinlets, the earlier sometimes without 

 blade; flowers long-jjcdicellate, mostly verticillate, in a loose raceme or 

 panicle, with lanceolate scarious bracts slightly connate at base. 



1. Alisina. Flowprs perfnrt, usually 6-androua. Carpels flattened, in one whorl. 



2. .Sa;;ittaria. Flowers mostly unisexual, atameua rarely few. Cari)els flattened, in 



dense heads, winged. 

 8. £chinodoru8. Flowers perfect. Stamens 6 or more. Cariiels wipiUitc, tur^jid and 

 ribbed, often beaked. 



