470 



LYTHRACEAE. 



[Vox,. 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 oo. Capsule globose, indehiscent, 2-celled. 

 [Greek, twice double.] 



A monotypic genus of east-central North America, closely related to the Old World genus 

 Pefilis I<. 



i. Didiplis diandra (Nutt.) Wood. Water 

 Purslane. (Fig. 2542.) 



CallitricheautumnalisCi) Michx. Fl. Bor. Am. 1:2. 1803. 



Not L. 1753- 



Peplis (?) diandra Nutt. ; DC. Prodr. 3: 77. 1828. 

 I>icii/>lis lintaris Raf. Atl. Journ. 177. 1833. 

 Didiplis diandra Wood. Bot. & Fl. 124. 18/0. 



Submersed or rooting in the mud on shores, gla- 

 brous, 3 '-i 2' long. Submersed leaves thin, elongated- 

 linear or lanceolate, acute or acuminate at the apex, 

 broader at the base, 6 // -io // long; emersed leaves 

 linear-oblong, narrowed at the base; flowers incon- 

 spicuous, about W long; capsule about W in diam- 

 eter. 



Minnesota and Wisconsin to Texas and Mexico, east to 

 North Carolina and Florida. Resembling Callitriche in 

 habit. June-Aug. 



3. ROTALA L. 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. 



i. Rotala ramdsior (L.) Koehne. 

 (Fig. 2543.) 



Rotala. 



Ammannia ramosiorl,. Sp. PI. 120. 1753. 

 Ammannia humilis Michx. Fl. Bor. Am. i: 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 // -i5 // long, 

 \"-T) f 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, s-y-toothed, with as many slender elongated acces- 

 sory teeth in the sinuses. Stamens ro, rarely 8, alternately longer and shorter, inserted on 



