470 LYTHRACEAE, [Vor II. 
2. DIDIPLIS Raf. Atl. Journ. 177. 1833. 
Aquatic or marsh plants, rooting in the mud, with 4-angled stems, opposite linear entire 
leaves, and very small axillary solitary green flowers. Calyx hemispheric or campanulate, 
4-lobed, with no accessory teeth. Petals none. Stamens 2-4, usually 4, inserted on the 
calyx-tube; filaments very short. Ovary globose, enclosed by the calyx, 2-celled; style 
scarcely any; stigma obscurely 2-lobed; ovules ©. Capsule globose, indehiscent, 2-celled. 
[Greek, twice double. ] 
A monotypic genus of east-central North America, closely related to the Old World genus 
Peplis I, 
1. Didiplis diandra (Nutt.) Wood. Water 
Purslane. (Fig. 2542.) 
Callitriche autumnalis (?) Michx. Fl. Bor. Am. 1:2. 1803. 
Not L. 1753. 
Peplis(?) diandra Nutt.; DC. Prodr. 3:77. 1828. 
Didiplis linearts Raf. Atl. Journ. 177. 1833. 
Didiplis diandra Wood. Bot. & Fl. 124. 1870. 
Submersed or rooting in the mud on shores, gla- 
brous, 3-12’ long. Submersed leaves thin, elongated- 
linear or lanceolate, acute or acuminate at the apex, 
broader at the base, 6’/-10’/ long; emersed leaves 
linear-oblong, narrowed at the base; flowers incon- 
spicuous, about 14’ long; capsule about 4’ in diam- 
eter. 
Minnesota and Wisconsin to Texas and Mexico, east to 
North Carolina and Florida. Resembling Cadli/riche in 
habit. June-Aug. 
3- ROTALA I. Mant. 2: 175. 1771. 
Low annual mainly glabrous herbs, usually with opposite sessile or sometimes petioled 
leaves, 4-angled stems, and axillary mainly solitary small flowers. Calyx campanulate or 
globose, 4-lobed. Petals 4 in our species. Stamens 4, short. Ovary free from the calyx, 
globose, 4-celled. Capsule globose, enclosed by the membranous calyx, 4-celled, septicidally 
dehiscent, the valves very minutely and densely striate transversely. [Latin, wheel, from 
the whorled leaves of some species. ] 
About 30 species, of wide geographic distribution in warm and tropical regions. In addition 
to the following, another may occur in the southwestern States. 
1. Rotala ramosior (L.) Koehne. Rotala. 
(Fig. 2543.) 
Ammannia ramosior I, Sp. Pl. 120. 1753. 
Ammannia humilis Michx. Fl. Bor, Am, 1:99. 1803. 
Boykinia humilis Raf. Aut. Bot. 9. 1840. 
Rotala ramosior Koehne, in Mart. Fl. Bras. 13: Part 2, 194. 1875. 
Glabrous, branched from the base or simple, ascending or 
erect, 2’-6’ high. Leaves oblong or linear-oblong, 6’’-15’ long, 
1//-3/’ wide, blunt at the apex, narrowed and sessile at the base 
or tapering into a short petiole, not auricled; flowers solitary or 
rarely 3 in the axils, very small; petals minute; style almost 
none. 
In swamps, Massachusetts to Florida, west to northern Illinois, 
Nebraska, Texas and Mexico. Also in California, Oregon, South 
America and the West Indies. July-Sept. 
4. DECODON J. F. Gmel. Syst. Veg. 2: 677. 1791. 
Herbaceous shrubs, with verticillate or opposite, short-petioled entire leaves, and showy 
purple pedicelled trimorphous flowers, in nearly sessile axillary cymes. Calyx broadly 
campanulate, or hemispheric, nerved, 5-7-toothed, with as many slender elongated acces- 
sory teeth in the sinuses. Stamens Io, rarely 8, alternately longer and shorter, inserted on 
