HYDROCHARITACEAE 69' 



Gener^ 14, species about 60; 6 genera and 8 to 10 species in the Philip- 

 pines. 



1. Fresh-water herbs. 



2. Stems branched, leafy, elongated, the leaves whorled 1. Hydrilla 



2. Stemless, or with stolons only. 

 3. Leaves very long and narrow, ribbon-like; perianth single. 



2. Vallisneria 

 3. Leaves broad, the floating ones up to 20 cm in width; perianth double. 



3. Ottelia 

 1, Salt-water herbs; stems slender, creeping. 



2. Stamens 3 4. Halophila 



2. Stamens 6 5. Thalassia 



1. HYDRILLA Richard 



An elongated, branched, leafy, submerged, herb. Leaves short, in whorls, 

 or the lower ones opposite. Male flowers solitary,- shortly pedicelled, in a 

 Eubglobose, sessile, mujricate spathe; sepals 3,' ovate, green; petals 3, oblong 

 or wedge-shaped; stamens 3, the anthers large, reniform. Female flowers 



1 or 2, sessile, in a tubular, 2-toothed spathe, the perianth as in the staminate 

 flowers but the segments narrower ; ovary produced beyond the spathe 

 in a filiform beak, 1-celled; styles 2 or 3. Fruit subulate, smooth or. 

 muricate, seeds 2 or 3, oblong. (From the Greek, with reference to its 

 habitat.) 



A monotypic genus. 



1. H. vertlclllata (Roxb.) Royle. Dlgman (Tag.). 



Submerged in still or slowly running water, forming large masses, often 



2 m long; Leaves 4 to 8 in a whorl, thin, narrowly oblong, serrulate, 0.5 to 

 1.5 cm long. Flowers about 0.5 cm long, the perianth very variable, the 

 male flowers escaping from the sheaths, when mature, and floating on the 

 surface of the water. 



Abundant in fresh-water esteros, and in the Mariquina River; widely 

 distributed in the Philippines. Europe through Asia to the Mascarene 

 Islands, Malaya, and Australia. 



2. VALLISNERIA Linnaeus 



Submerged, tufted, stemless, stoloniferous, herbaceous, the leaves very 

 long, thin, linear. Male flowers very numerous, minute, in an ovoid, 3-lobed, 

 shortly peduncled spathe; sepals 3; petals none; stamens 1 to 3. Femafe 

 flowers solitary, in a tubular, 3-toothed spathe, terminating a verjf long, 

 filiform, spiral scape ; perianth as in the male flowers. Fruit linear, included 

 in the spathe, many-seeded. (In honor of A. Vallisneri, an early Italian 

 botanist.) 



A genus with three or four species in all warm regions. 



1. V. gigantea Grafebn. Sintas (Tag.) (From Sp. oiMta=rifcbon) ; Eel Grass. 

 Leaves often 2 m or more in length, or sometimes 0|nly a few cm, 

 according to the depth of/ the water, thin, 1 cm wide or less. Staminate 

 spathes about 0.5 cm long: when the flowers emerge they break off, rise to 

 and float on the surface of the water. Female spathes floating on the 

 surface of the water at the time the flowers are open, but after fertilization 

 the scape coils up and draws the ovary down to ripen under water. 



