AMARANTHACEAE (AMARANTH FAMILY) 171 



2. Amaranthus hybridus L. Sp. PI. 990. 1753. Very similar, but slender 

 and with smaller leaves, darker green or purplish: spikes linear-cylindric, 

 axillary and forming crowded terminal panicles, ascending or somewhat 

 spreading or drooping: sepals oblong, acute or cuspidate. Like the preceding, 

 naturalized from tropical America and now widely distributed. 



3. Amaranthus spinosus L. Sp. PL 991. 1753. Stem stout and rigid, 

 freely branched, 3-10 dm. high: leaves ovate to lanceolate, tipped with the 

 excurrent midrib and bearing a pair of rigid stipular spines in the axils: flow- 

 ers in terminal spikes and axillary clusters : the subulate bracts, 1-nerved se- 

 pals, and the thin imperfectly circumscissile utricle subequal. Infrequent 

 weed in our range. 



4. Amaranthus Powellii Wats. Am. Acad. 10: 347. 1875. Glabrous, erect 

 and slender, with ascending branches and spikes, reddish, 5-8 dm. high or 

 more: leaves thin, 2-several cm. long, oblong to narrowly lanceolate, on slen- 

 der petioles: terminal compound spike erect, narrow and somewhat leafy; 

 bracts solitary, subulate, rigid, pungent: utricle equaling the oblong obtuse 

 sepals: seed orbicular, 1 mm. broad. (A. Wrightii Wats. 1. c. 12: 275.) 

 Colorado, in the Arkansas Valley. 



5. Amaranthus graecizans L. Sp. PI. 990. 1753. A pale glabrous annual, 

 with whitish stems; diffusely branched from the base: leaves oblong-spatulate 



' to obovate, obtuse or retuse: flowers polygamous in small axillary clusters; 

 bracts subulate, rigid, pungently awned, the lateral ones much smaller or 

 wanting: utricle rugose, exceeding the 3 membranous sepals: seed less than 

 1 mm. broad. A. albus L. Known as TUMBLEWEED, since it is freely up- 

 rooted when mature and driven about on the plains by the wind. 



6. Amaranthus blitoides Wats. Proc. Am. Acad. 12: 273. 1876. Branched 

 from the base; the branches prostrate, forming mats: leaves small, 5-20 mm. 

 long, obovate-spatulate, tapering into the slender petiole: spikelets short; 

 bracts ovate-oblong, short-acuminate, nearly equal: utricle not rugose: seed 

 about 1 mm. broad. A very troublesome weed in waste and cultivated 

 ground. 



7. Amaranthus Torreyi (Gray) Benth., Wats. Bot. Cal. 2: 42. 1880. Gla- 

 brous, erect, with grooved stem, 3-8 dm. high: leaves mostly lanceolate, 

 narrowed to an obtuse apex: flowers either monoecious or dioecious, in slen- 

 der terminal spikes and in axillary clusters : sepals of the sterile flowers oblong- 

 lanceolate, acute; the fertile obovate-spatulate, entire, retuse or emarginate, 

 deciduous with the indehiscent utricle: bracts cuspidate, scarcely equaling 

 the fruit. Colorado and southward. 



8. Amaranthus Palmeri Wats. Proc. Am. Acad. 12: 274. 1876. Somewhat 

 pubescent above, stout, branching, 5-8 dm. high: leaves oblong-rhomboid, 

 3-5 cm. long, equaled by the petiole, the upper reduced and narrow: spikes 

 elongated-linear, leafy at base; bracts solitary, rigid, narrowed into an awn: 

 flowers dioecious: sepals 5, spatulate, half as long as the bracts: utricle dry, 

 indehiscent. Rare in our range; to be expected in southern Colorado. 



2. ACNIDA L. WATER HEMP 



Ours an annual glabrous herb, with alternate petioled pinnately- veined 

 long-petioled leaves. Flowers dioecious, small, green, 3-bracted, in elongated 

 spikes. Staminate flowers of 5 thin oblong and mucronate sepals, longer than 

 the bracts, and as many stamens with oblong anthers; the cells of the latter 

 united only at the middle. Pistillate flowers with lance-subulate bracts longer 

 than the ovary; the calyx wanting. Fruit a thin membranous utricle, smooth 

 and even. Seed erect, smooth and shining. 



1. Acnida tamariscina (Nutt.) Gray, Am. Nat. 10: 489. 1876. Tall and 

 erect, with slender flexuous branches, often 1 or 2 m. high: flowers in elongated 

 panicled spikes: utricle indehiscent, ovoid, somewhat tubercled: stigmas very 

 long, divergent, plumose-hispid. A. tuberculata. Low wet sandy shores; 

 rare in our range; Colorado and southeastward. 



