HYDROCHARITACEAE 47 



submerged and maturing under water. Seeds with a straight embryo, without 

 endosperm. 



Staminate flowers with 1-3 stamens. 



Spathes of pistillate flowers sessile or nearly so, of 2-3 distinct bracts. 1. HALOPHILA. 



Spathes of pistillate flowers very long peduncled, of several more or less united 



bracts. 2. VALLISNERIA. 



Staminate flowers with 9 stamens. 3. PHILOTRIA. 



1. HALOPHILA Thouars. 



Marine herbs, with creeping rootstocks. Leaves opposite or whorled at the nodes, 

 accompanied by stipule-like scales. Flowers dioecious, solitary in spathes, 2 or 3 distinct 

 bracts arising between the leaves. Staminate flowers pedicelled : perianth of 3 rather 

 herbaceous sepals. Stamens 3 : anthers nearly sessile, extrorse. Pistillate flowers sessile 

 in the spathes : perianth of 3 minute sepals. Ovary 1-celled, with 3 parietal placentae, 

 long-beaked. Style 3-parted : branches filiform. Fruit included in the spathe. Seeds 

 numerous. Embryo with spirally bent cotyledons. 



1. Halophila Engelmannii Aschers. Floating, glabrous. Rootstocks branched, 

 with many nodes : stems 10 cm. long, or shorter, commonly erect : leaves mainly whorled 

 at the ends of the stem or its branches ; blades linear, oblong or oblanceolate, 1-3 cm. 

 long, obtuse or acutish, sharply serrulate, 3-nerved, sessile : flowers and fruit not known. 



In coves and creeks, peninsular Florida. Spring to winter. 



2. VALLISNERIA L. 



Acaulescent submerged herbs, very delicate. Leaves basal : blades several-nerved, 

 ribbon-like. Flowers dioecious. Staminate minute, numerous, crowded on a spadix 

 enclosed in a spathe of 3 segments. Perianth of 3 sepals. Stamens 2 or 1-3. Pistillate 

 flowers solitary at the ends of elongated cord-like spiral scapes, subtended by a tubular 

 2-cleft spathe: petals 3, larger than the 3 green sepals. Ovary 1-celled, inferior, with 3 

 parietal placentae: stigmas 3, each 2-lobed. Fruit elongated, leathery, indehiscent. 



1. Vallisneria spiralis L. Stoloniferous, flaccid, glabrous : leaf-blades narrowly 

 linear, 1-18 dm. long, entire or serrate below the apex : flowers inconspicuous ; Staminate 

 basal, detached at maturity, floating and expanding on the surface ; pistillate floating, 

 attached to the base of plant by elongated filiform scapes, which after fertilization coil 

 spirally and submerge the flower : spathes cylindric, 1-2 cm. long, subtending one flower, 

 membranous : fruit cylindric, 3-15 cm. long. 



In ponds or flowing water, New Brunswick to Minnesota, Florida and Texas. Summer and fall. 

 EEL-GRASS. TAPE-GRASS. 



3. PHILOTRIA Raf. 



Caulescent submerged herbs, with slender rootstocks and branching stems. Leaves 

 numerous, opposite or whorled : blades 1-nerved. Flowers polygamous or dioecious, from 

 a sessile 2-cleft spathe. Sepals 3. Petals 3, thin. Staminate flowers minute, with 9 sta- 

 mens. Fertile flowers pistillate or perfect : stamens 3-6, sometimes sterile. Ovary 

 1-celled, with 3 parietal placentae. Stigmas apparently sessile, 2-lobed. Ovules few. 

 Fruit leathery, inhehiscent. [Elodea Michx., not Elodes Adans.] WATER-WEED. 



Leaf-blades oblong, elliptic or ovate-oblong : calyx over 2.5 mm. broad. 1. P. Cnnadensis. 



Leaf-blades narrowly linear or narrowly linear-lanceolate: calyx less than 2.5 mm. 



broad. 2. P. minor. 



1. Fhilotria Canadensis (Michx.) Britton. Aquatic, flaccid. Stems variable in 

 length, 1-12 dm. long, forking : leaves opposite or in whorls of 3 or 4 above the base ; 

 blades oblong, elliptic or ovate-oblong, 4-15 mm. long, entire or serrulate ; whorls often 

 approximate : flowers axillary ; Staminate submerged, breaking off at maturity and floating 

 on the surface they discharge the pollen near the pistillate flowers, these floating, attached 

 to the plant by the elongated stalk, which varies from 3-30 cm. in length : spathes 10-18 

 mm. long. \_Elodea Canadensis Michx.] 



In ponds and slow-flowing water, nearly throughout North America. Spring to fall. 



3. Philotria minor (Engelm. ) Small. Similar to P. Canadensis in habit, but more 

 slender, with more branched stems and less densely crowded leaves. Leaf -blades narrowly 

 linear or narrowly linear-lanceolate : pedicels hair-like : calyx 1.5-2iiim. broad. 



In ponds and streams, Minnesota to Tennessee, Missouri and Arkansas. Summer. 



