1824.

Monoecious herbs or shrubs, perennial by rootstocks, silky or pilose, the sap purplish. Leaves alternate, entire, or rarely toothed, often strongly nerved. Flowers in axillary or axillary and terminal clusters, often racemed, usually bracted. Staminate flowers often crowded at the ends of the racemes; calyx 4-5-lobed, the lobes valvate; petals 4 or 5, alternate with the calyx-lobes and with the lobes of the disk; stamens of the same number as the petals or two or three times as many, united into a column. Pistillate flowers with the calyx-lobes imbricated and smaller petals, the ovary 3-celled, each cavity with 1 ovule; styles 3, short, once to thrice cleft. Capsule 3-lobed, depressed, separating into 3 2-valved carpels. Seeds subglobose, wrinkled, or muricate, sometimes crested; embryo straight in the fleshy endosperm. [Greek, double-ranked, in allusion to the stamens.]

About 20 species, natives of temperate and tropical regions. Type species: Ditaxis fascicu-lata Vahl.

Flowers in terminal and axillary racemes; leaves sessile.

1.

D. mercurialina.

Flowers in axillary clusters; leaves short-petioled.

2.

D. humilis.

1. Ditaxis Mercuriálina (Nutt.) Coult. Tall Ditaxis

Fig. 2719

Aphora mercurialina Nutt. Trans. Am. Phil. Soc. (II.)

5: 174. 1833-37. Argyrothamnia mercurialina Muell. Arg. Linnaea 34:

148. 1865. Ditaxis mercurialina Coult. Mem. Torr. Club 5: 213.

1894.

Stem slender, strict, usually simple, channeled, silky, 4'-2° high. Leaves alternate, ovate to narrowly lanceolate, 10"-2' long, undulate, sessile, often strongly 3-nerved, glabrate; flowers in terminal and axillary racemes; staminate flowers with lanceolate or linear-lanceolate acute ciliate calyx-segments, and spatulate-oblong undulate petals; pistillate flowers with a 5-parted calyx, the segments lanceolate, spreading, 3 times as long as those of the staminate, petals none; capsule depressed, 3"-4 1/2" in diameter, somewhat silky, 3-lobed; seeds globose-ovoid, 2" long, pointed, wrinkled, indistinctly 2-crested.

In dry soil, Kansas and Arkansas to Texas. Lower leaves sometimes oblanceolate. April-July.

1 Ditaxis Mercuri Lina Nutt Coult Tall Ditaxis 1061

2. Ditaxis Hùmilis (Engelm. & Gray) Pax. Low Ditaxis

Fig. 2720

Aphora humilis Engelm. & Gray, Bost. Journ. Nat.

Hist. 5: 262. 1847. Argyrothamnia humilis Muell. Arg. Linnaea, 34:

147. 1865. Ditaxis humilis Pax in Engl. & Prantl, Nat Pfl. Fam.

3: Abt. 5, 45. 1890.

Stem slender, much branched, pubescent, the branches spreading, 4'-1° long. Leaves alternate, ovate, oblong, obovate or oblanceolate, 5"-15" long, entire, narrowed into a short petiole; flowers in axillary clusters; staminate flowers with petals a little longer than the 5 calyx-segments and longer than the lobes of the disk; pistillate flowers with a 5-parted calyx and 3 styles each usually twice 2-cleft; capsule short-pedicelled, much depressed, 2"-3" in diameter, 3-4-lobed; seeds oval-globose, about 1" long, muricate.

Prairies, Kansas to Louisiana and Texas. March-Sept.

2 Ditaxis H Milis Engelm Gray Pax Low Ditaxis 1062