Genus 2. 



LOOSESTRIFE FAMILY. 



579 



2. DIDIPLIS Raf. Atl. Journ. 177. i«33. 



An aquatic or marsh plant, rooting in the mud, with 4-angIed stems, opposite linear entire 

 leaves, and very small axillary solitary green flowers. Calyx hemispheric or campanulate, 

 4-lobed, with no appendages. 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 =0. Capsule globose, indehiscent, 2-celled. [Greek, 

 twice double.] 



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

 Peplis L. 



Didiplis diandra (Nutt.) Wood. .Water 

 Purslane. Fig. 3001. 



Callilriche autumnalis{?) Michx. Fl. Bor. Am. i: 2. 1803. 



Not L. 1753. 

 PeplisCi) diandra Nutt.; DC. Prodr. 3: 77. 1828. 

 Didiplis linearis Raf. Atl. Journ. 177. 1833. 

 Didiplis diandra Wood. Bot. & Fl. 124. 1870. 



Submersed or rooting in the mud on shores, glabrous, 

 3'-l2' 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 inconspicuous, about i" 

 long; capsule about i" in diameter. 



Minnesota and Wisconsin to Texas and Mexico, east to 

 North Carolina and Florida. Resembling Callilriche 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, the sinuses appendaged. 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. Type species : 

 Rotala verticillaris L. 



I. Rotala ramosior (L.) Koelme. 

 Fig. 3002. 



Tooth-cup. 



Ammannia ramosior L. 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, 

 2-13' high. Leaves oblong or linear-oblong, 6"-is" long, 

 i"_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, Minnesota, Nebraska, Arkan- 

 sas, Texas and Mexico. Also in California, Oregon, South America 

 and the West Indies. July-Sept. 



4. DECODON J. F. Ginel. 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 cam- 

 panulate, or hemispheric, nerved, 5-7-toothed, with as many slender elongated accessory 

 teeth in the sinuses. Stamens 10, rarely 8, alternately longer and shorter, inserted on the 



