TAPE-GRASS FAMILY. 93 
1. PHILOTRIA Raf. Am. Month. Mag. 2: 175. 1818. 
[ELopEa Michx. Fl. Bor. Am. 1: 20. 1803. Not £/odes Adans. 1763. ] 
: (Upora Nutt. Gen. 2: 242, 1818.] 
Stems submerged, elnogated, branching, leafy. Leaves opposite or whorled, crowded, 
r-nerved, pellucid, minutely serrulate or entire. Flowers dioecious or polygamous, arising 
from an ovoid or tubular 2-cleftspathe. Perianth 6-parted, at least the 3 inner segments peta- 
loid. 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 8 species, inhabitants of fresh water ponds and streams in temperate and tropical America. 
1. Philotria Canadénsis (Michx.) Britton. Water-weed. Ditch-moss. 
Water Thyme. (Fig. 207.) 
Elodea Canadensis Michx. Fl. Bor. Am. 1:20. 1803. 
Anacharis Canadensis Planch. Ann. Sci. Nat. (III. 9: 
75. 1849. 
Philotria Canadensis Britton, Science (II.) 2:5. 1895. 
Stems 4/-3° long, according to the depth of water. 
Leaves linear or elliptic, acute or obtuse, serrulate or 
entire, verticillate in 3’s or 4’s or the lower opposite, 
2//-7/’ long, %4’/-2’’ wide; flowers axillary, white, the 
staminate minute, sessile, breaking 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 of the water which 
they reach by means of the slender calyx-tube which 
varies in length from 2’—1°, their spathes 5’’-7’’ long; 
stigmas spreading, papillose or pubescent. 
Nearly throughout North America, except the extreme 
north. Naturalized in Europe. It has been maintained 
that there are four North American species. May—Aug. 
2. VALLISNERIA L, Sp. Pl. 1015. 1753. 
Aquatic dioecious submerged perennials, with long grass-like floating leaves. Stam- 
inate 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). Pistillate flowers on a very long 
flexuous or spiral scape, with a tubular, 2-cleft, 1-flowered spathe ; perianth-tube adnate to 
the ovary, 3-lobed and with 3 small petals; ovary 1-celled with 3 parietal placentae ; stigmas 
3, nearly sessile, short, broad, 2-toothed with a minute process just below each sinus ; ovules 
unmerous, 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. 
1. Wallisneria spiralis L. Tape- 
grass. Eel-grass. (Fig. 208. ) 
Vallisneria spiralis \,. Sp. Pl. 1015. 1753. 
Plant rooting in the mud or sand, stolon- 
iferous. Leaves thin, narrowly linear, 5- 
nerved, obtuse, sometimes serrate near the 
apex, %°—6° long, 2/’-9” wide, the 2 marginal 
nerves faint; the staminate bud separates from 
the scape at the time of flowering and ex- 
pands upon the surface of the water; pistil- 
late flowers upon a long thread-like scape, 
the spathe %/’-1’ long, enclosing a single 
white flower; ovary as long as the spathe; 
after receiving the pollen from the staminate 
flowers the scape of the pistillate contracts 
spirally ; ripe fruit 2’-7’ long. 
In quiet waters, New Brunswick to Florida, 
west to Minnesota, lowaand Texas. The “wild 
celery’’ of Chesapeake Bay, and a favorite food 
of the canvas-back duck. Aug.—Sept. 
