430 LEMNACE^E. (DUCKWEED FAMILY.) 



idle larger, consisting of numerous sessile pistils, each surrounded by 3 - G scales 

 much like a calyx. Fruit nuUike when mature. Roots fibrous. Stems sim- 

 ple or branching, sheathed below by the base of the linear leaves. (Name from 

 trnapyavov, a fillet, from the ribbon-like leaves.) 



# Inflorescence mostly branched, with numerous heads, the 1-3 lower fertile, the rest 

 sterile: stigmas often 2, linear, much longer than the style: stems stout, erect (2- 

 3 high) : leaves erect (' - 1' wide), flat and merely keeled, the base triangular with 

 concave sides : fruit sessile. 



1. S. eiirycarplim, n. sp. Engelm. Fruit many-angled (3" -4" long), 

 with a broad and depressed or retuse summit (2" wide), abruptly and slightly tipped 

 in the centre; head globose, 1' wide when ripe. Borders of ponds, &c., com- 

 mon northward and especially westward. June - Sept. 



2. S. raiiiosinii, Hudson. Fruit somewhat triangular, with the summit 

 hemispherical and pointed, smaller than in the last. Same situations, northward 

 and eastward. July -Sept. (En.) 



# * Inflorescence mostly simple : stigma single : stem slender. 



3. S. Simplex, Hudson. Fertile and sterile heads each 3 or 4, the latter 

 or some of them mostly peduncled ('-' broad) ; fruit abruptly contracted at the 

 summit into a slender beak as long as itself; stigma linear; leaves triangular at 

 the base with flat sides (6' - 1 8' long) . ( S. Americanum, Nult. ) Along streams 

 and pools; common northward and eastward. (Eu.) 



4. S. natans, L., var. affine, Fries. Heads few, the'fertile 1-3; stig- 

 ma short ; fruit oblong, slender-beaked as in No. 3, also attenuate into a stalk-like 

 base; leaves very long and flaccid, floating. (S. affine, Schnitzlein.) In ponds and 

 slow streams, New England, New York, and northward. This may be the S. 

 angustifolium of Michaux, as is generally thought; but Fries assigns that to 

 the next. (Eu.) 



5. S. ail gUSti folium, Michx. Small and slender ; fruit more triangu- 

 lar, scarcely beaked, short-pointed, not contracted at the base ; leaves long and nar- 

 row (l^"-2" wide) and floating when growing in water, scarcely surpassing the 

 stems in dwarf states growing nearly out of water (5' -8' high). New England 

 to Wisconsin and northward. Fruiting heads only 2" - 3" in diameter. (Eu.) 



ORDER 114. LEMNACEJE. (DUCKWEED FAMILY.) 



Minute stemless plants, floating free on the water, destitute of distinct stem 

 and foliage, being merely a flat frond, producing few monoecious flowers from 

 a chink at the edge or upper surface, and usually hanging roots from under- 

 neath : ovules erect from the base of the cell. Fruit a 1- 1 -seeded utricle. 

 Embryo straight, in the axis of fleshy albumen. A little group of plants, 

 of peculiar mode of growth, in character mostly intermediate between the 

 Arum Family and the following, to one or the other of which it may be 

 joined. The Linnaean genus Lemna has been divided into three genera, 

 (answering to the following sections,) possibly with sufficient reasons ; but 

 it is not worth while to adopt them here, since the flowers ar d fruit are 

 rarely met with. 



