6b FLORA. 



i. PHILOTRIA Raf. [ELODEA Michx.] 



Stems submerged, elongated, branching, leafy. Leaves opposite or whorled, 

 crowded, I -nerved, pellucid, minutely serrulate or entire. Flowers dioecious or 

 polygamous, arising from an ovoid or tubular 2 -cleft spathe. Perianth 6-parted, 

 at least the 3 inner segments petaloid. Staminate flowers with 9 stamens, the 

 anthers oblong, erect. Ovary I -celled with 3 parietal placentae. Stigmas 3, 

 nearly sessile, 2-lobed. Fruit oblong, coriaceous, few-seeded. [Name from the 

 Greek, referring to the leaves, which are often whorled in threes.] About 10 

 species, inhabitants of fresh-water ponds and streams in temperate and tropical 

 America. 



i. Philotria Canadensis (Michx.) Britton. WATER-WEED. DITCH-MOSS. 

 WATER THYME. Stems o. i-i m. long. Leaves linear or elliptic, acute or 

 abtuse, serrulate or entire, vcrticillate in 3's or 4's or the lower opposite, 4-15 mm. 

 long, 1-4 mm. wide; flowers axillary, white, the staminate minute, sessile, break, 

 ing off at the time of flowering and rising to the surface where they shed their 

 pollen around the pistillate ones; pistillate flowers expanding on the surface, which 

 they reach by means of the slender calyx-tube, which varies in length from 5-25 

 cm., their spathes 10-15 mm. long; stigmas spreading, papillose or pubescent. 

 Nearly throughout N. Am., except the extreme north. Naturalized in Europe. 

 It has been maintained that there are four N. Am. species. May-Aug. 



The p^ant of the northern lakes and rivers, with ovate or oval leaves, is appar- 

 ently the type of the species. The plant of the Atlantic States with lanceolate or 

 linear-lanceolate leaves is the Serpicula vertidllata angustifolia Muhl. (I. F. f. 207); 

 that of the Central States from Minn, to Ky. and Mo., with leaves similar to this, 

 but pellucid, and the stems shorter, is Udora Canadensis minor Engelm. These 

 three appear to be distinct, but for lack of flowers and fruit in the material at my 

 command, I am at present unable to characterize them further. 



2. VALLISNERIA L. 



Aquatic dioecious submerged perennials, with long grass-like floating leaves. 

 Staminate flowers with a 2-3 -parted spathe on a short scape, numerous, nearly 

 sessile on a conic receptacle; perianth 3 parted; stamens generally 2 (1-3). Pis- 

 tillate flowers on a very long flexuous or spiral scape, with a tubular, 2-cleft, 

 I -flowered spathe; perianth-tube adnate to the ovary, 3-lobed and with 3 small 

 petals; ovary l-cel!ed with 3 parietal placentae; stigmas 3, nearly sessile, short, 

 broad, 2 -toothed with a minute process just below each sinus; ovules numerous, 

 borne all over the ovary -wall, orthotropous. Fruit elongated, cylindric, crowned 

 with the perianth. [Named for Antonio Vallisneri, 1661-1730, Italian naturalist.] 

 A monotypic genus of wide distribution both in the Old World and the New. 



i. Vallisneria spiralis L. TAPE-GRASS. EEL-GRASS. (I. F. f. 208.) Plant 

 rioting in the mud or sand, stolon iferous. Leaves thin, narrowly linear, 5 -nerved, 

 obtuse, sometimes serrate near the apex, 0.2-2 m. long, 4-18 mm. wide, the 2 

 marginal nerves faint; the staminate bud separates from the scape at the time of 

 flowering and expands upon the surface of the water; pistillate flowers upon a 

 long thread like scape, the spathe 12-25 mm. long, enclosing a single white 

 flower; ov.iry as long as the spathe; after receiving the pollen from the staminate 

 flowers the scape of the pistillate contracts spirally; ripe fruit 5-17 cm. long. In 

 quiet waters, N. B. to Fla., Minn., Iowa and Tex. The "wild celery" of Chesa- 

 peake Bay, and a favorite food of the canvas-back duck. Aug.-Sept. 



3. LIMNOBIUM L. C. Richard. 



Aquatic, stoloniferous herbs, the leaves fascicled at the nodes, petioled, broad,, 

 often cordate. Flowers monoecious, white, from sessile or stipitate, 2-leaved, 

 membranous spathes. Perianth 6-parted, the segments petaloid, the 3 outer 

 oblong-oval, the 3 inner oblong-linear. Staminate flowers 2-4 in a spathe, long- 

 peduncled, the stamens united in a column bearing 6-12 anthers at different 

 heights, sometimes producing only 9-12 staminodia, the filaments tipped with 

 abortive anthers. Pistillate flowers sessile or short-ped uncled with 3-6 vestigial 

 stamens; ovafy 6-9-celled with as many central placentae; stigmas as many as the 



