HYDROCHARITACEAE 69 
Genera 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. 
8. Leaves very long and narrow, ribbon-like; perianth single. 
2. Vallisneria 
8. Leaves broad, the floating ones up to 20 cm in width; perianth double. 
3. Ottelia 
1. Salt-water herbs; stems slender, creeping. 
EO RES 2S Se a Re ee) 4. Halophila 
ST OS es Se GO RSS Pe Se ee oe ae» 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 
subglobose, sessile, muricate 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. verticillata (Roxb.) Royle. Digman (Tag.). 
Submerged in still or slowly running water, forming large masses, often 
2mlong. Leaves 4 to 8 in a whorl, thin, narrowly oblong, serrulate, 0.5 to 
1.5 em 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. Female 
flowers solitary, in a tubular, 3-toothed spathe, terminating a very 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 Graebn. Sintas (Tag.) (From Sp. cinta=ribbon) ; Eel Grass. 
Leaves often 2 m or more in length, or sometimes only 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. 
