342 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 alternatej 

 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 septicldally 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. iiidica 



1. R. mexicana C. & S. subsp. pusiila (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 ^, rarely 4. Cap- 

 sule 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 ap- 

 pendages 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. 



