L Y THRA CEA E. 649 



tube; filaments very short. Ovary globose, 2-celled; style scarcely any; stigma 

 obscurely 2-lobed; ovules oo . Capsule 2-celled. [Greek, twice double.] A 

 monotypic genus of east-central N. Am. 



i. Didiplis diandra (Nutt.) Wood. WATER PURSLANE. (I. F. f. 2542.) 

 Submersed or rooting in the mud, 0.7-3 dm. l n g- Submersed leaves thin, elon- 

 gated-linear or lanceolate, acute or acuminate at the apex, broader at the base, 

 12 cm. long; emersed leaves linear-oblong, narrowed at the base; flowers about 

 i mm. long; capsule about I mm. in diameter. Minn, and Wis. to Tex. andMex., 

 N. Car. and Fla. Resembling Callitriche in habit. June-Aug. 



3. ROTALA L. 



Low annual mainly glabrous herbs, usually with opposite leaves, 4-angled stems, 

 and axillary mainly solitary small flowers. Calyx campanulate or globose, 4-lobed. 

 Stamens 4, short. Ovary free from the calyx, globose, 4-celled. Capsule glo- 

 bose, 4-celled, the valves minutely and densely striate transversely. [Latin, wheel, 

 from the whorled leaves of some species.] About 30 species, of wide distribution. 



i. Rotala ramosior (L.) Koehne. ROTALA. (I. F. f. 2543.) Glabrous, 

 5-25 cm. high. Leaves oblong or linear-oblong, 1-3 cm. long, blunt at the apex, 

 narrowed and sessile at the base or tapering into a short petiole, not auricled ; flow- 

 ers solitary or rarely 3 in the axils, very small ; petals minute ; style almost none. 

 In swamps, Mass, to Fla., 111., Neb., Tex. and Mex. Also in Cal., Ore., S. Am. 

 and the W. Indies. July-Sept. 



4. DECODON J. F. Gmel. 



Herbaceous shrubs, with verticillate or opposite, short- petioled entire leaves, and 

 showy purple trimorphous flowers, in nearly sessile axillary cymes. Calyx broadly 

 campanulate, 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 calyx-tube, the longer exserted. Style filiform; stigma small. 

 Capsule globose, 3-5-celled, included in the calyx, loculicidally dehiscent. [Greek, 

 ten-toothed, referring to the calyx.] A monotypic genus of eastern N. Am. 



i. Decodon verticillatus (L.) Ell. SWAMP LOOSESTRIFE OR WILLOW- 

 HERB. (I. F. f. 2544.) Aquatic, somewhat woody, with angular recurved gla- 

 brous or slightly pubescent stems, 13 m. long, which root from the tip when they 

 reach the water or mud. Leaves lanceolate, 5-13 cm. long, glabrous above, some- 

 what pubescent beneath, acute at both ends; petioles 4-8 mm. long; flowers nearly 

 2.5 cm. broad; petals cuneate at the base; capsule about 5 mm. in diameter. In 

 swamps, Me. to Fla., Ont., Minn., Ky. and La. Stems clothed with cerenchyma 

 at the base. July-Sept. 



5. LYTHRUM L. 



Herbs or shrubs, with 4-angled stems, entire leaves, and often dimorphous or 

 trimorphous flowers. Calyx-tube 8-12-ribbed, straight, with 46 primary teeth 

 and an equal number of accessory ones in the sinuses. Petals 4-6, usually obovate, 

 rarely wanting. Stamens 8-12, inserted on the calyx-tube. Ovary oblong, ses- 

 sile, 2-celled; style filiform; stigma mostly capitate; ovules numerous. Capsules 

 enclosed by the calyx, membranous, 2-celled, 2-valved, or bursting irregularly. 

 [Greek, gore, from the purple flowers.] About 23 species, of wide distribution. 

 Besides the following, about 4 others occur in the southern and western U. S. 



Flowers axillary, solitary; stamens not more numerous than petals. 

 Leaves mostly alternate. 



Leaves obtuse ; stamens all included; annual. i. Z,. Hyssopifolia. 



Leaves acute; stamens of short-styled flowers exserted; perennial. 



2. L. alatum. 

 Leaves mostly opposite. 



Leaves narrowly linear, narrowed at the base. 3. Z. lineare. 



Leaves ovate or oval, rounded or cordate at the base. 4. L. Vulneraria. 



Flowers in panicled spikes, terminal; stamens twice as many as petals. 



5. L. Salicaria. 



i. Lythrum Hyssopifolia L. HYSSOP LOOSESTRIFE. GRASS POLY. (I. F. 

 f. 2545.) Glabrous, pale green, 1.5-6 dm. high. Leaves sessile, mainly alter- 



