A flora of Manila - Rainforestation

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A FLORA OF MANILA
3. ROTALA Linnaeus
Erect, low, simple or branched, annual herbs growing in wet places,
glabrous or nearly so. Leaves decussate or verticillate, rarely alternate,
sessile or subsessile. Flowers 3- to 6-merous, small, mostly sessile, axillary
and solitary, or in axillary spikes or racemes, usually 2-bracteolate. Calyx
campanulate to hemispheric, 3- to 6-lobed, the lobes usually with a setiform
appendage. Petals small. Stamens 1 to 6. Ovary sessile or subsessile;
style short or elongated. Capsules septicidally 2- to 4-valved, carti-
laginous, the walls densely and minutely horizontally striate under a
lens. (Probably from Latin "wheel" in reference to the verticillate leaves
of most species.)
Species 38, chiefly in tropical Asia and Africa, a few in Australia,
Europe, and America, 4 in the Philippines.
1. Leaves verticillate; petals none 1. R. mexicana
1. Leaves opposite; petals present.
2. Flowers axillary, solitary 2. R. ramosior
2. Flowers in axillary spikes 3. R. indica
1. R. mexicana C. & S. subsp. pusilla (Tul.) Koehne.
A small, glabrous, erect, annual plant usually less than 3 to 4 cm
in height, generally branched from the base. Leaves linear-oblong, in
threes or fours, somewhat close, 5 mm long or less, obtuse, truncate, or
2-pointed. Flowers axillary, solitary, less than 1 mm long, 4- or 5-merous,
the calyx-teeth triangular. Petals none. Stamens 2 or 3, rarely 4. Capsule
subglobose, about 1 mm in diameter.
In old rice paddies, Caloocan, San Juan del Monte, etc., fl. Oct.-Nov.;
of very local occurrence in the Philippines. The subspecies in tropical
Asia and Africa, the species in one form or another in most tropical
countries.
2. 4. R. RAMOSIOR (L.) Koehne.
An erect, slender, simple or branched, glabrous plant 8 to 25 cm high,
the stems somewhat 4-angled, usually purplish. Leaves oblanceolate to
linear-lanceolate, 1.5 to 3 cm long, obtuse, base narrowed to the short
petiole. Flowers small, axillary, solitary, sessile, the bracteoles about
as long as the calyx, at time of flowering 2.5 to 3 mm long, the appendages
longer than the lobes, spreading, lanceolate-acuminate, the lobes
triangular-ovate, acute or acuminate. Petals elliptic or oblong-elliptic,
pale-pink, about 1 mm long. Capsule ovoid, 3 to 4 mm long.
In open wet grass lands, fl. Oct.-Dec. ; widely distributed in the Phil-
ippines. A native of North and South America, introduced in the Phil-
ippines, now widely distributed and thoroughly naturalized.
3. R. Indica (Willd.) Koehne.
An erect, simple or branched, glabrous, annual herb 6 to 35 cm high,
the stems obscurely 4-angled. Leaves sessile or subsessile, oblong, elliptic,
or obovate, 8 to 15 mm long, acute or obtuse and mucronate, nerves
prominent on the lower surface, margins cartilaginous. Spikes axillary,
solitary, numerous, 8 to 15 mm long, the flowers numerous, in the axils
of much-reduced leaves, or sometimes the spikes wanting and the flowers
strictly axillary in the axils of normal leaves. Flowers subsessile. Calyx
2 to 2.5 mm long, subcampanulate, green, the lobes lanceolate, acuminate.