A MA R ANTH ACE AE 39 1 



B. Sepals not abruptly contracted into claws. 

 Utricle circumscissile. 



Flowers, at least the upper ones, in dense terminal spikes. 

 Stems unarmed, without spines at the leaf-axils. 



Stamens 3. 5. A. Powellii. 



Stamens 5. 



Spikes strict : sepals mostly obtuse. 6. A. retroflexus. 



Spikes drooping : sepals mostly acute. 7. A. hybridus. 



Stems furnished with a pair of spines at each leaf-axil. 8. A. spinosus. 



Flowers in small axillary clusters usually surpassed by the leaves. 



Sepals 4 or 5 : stems prostrate : seeds 1.5-2 mm. long. 9. A. Uitoides. 



Sepals 3 : stems erect : seeds about 1 mm. long. 10. A. afbus. 



Utricle indehiscent. 



Flowers, at least the upper ones, in continuous or interrupted spikes. 



Utricle rugose : stems erect. 11. A. viridis. 



Utricle prominently 3-5-ribbed : stems spreading or decumbent. 12. A, deftexus. 



Flowers in axillary clusters surpassed by the leaves. 



Pedicels conspicuously thickened. 13. A. crasstpes. 



Pedicels not tnickened. 



Stems elongated : seeds less than 1 mm. long. 14. A. emarginatus. 



Stems abbreviated : seeds fully 2 mm. long. 15. A. pumilus. 



1. Amaranthus Berlandteri (Moq. ) Uline & Bray. Foliage deep green. Stems 

 erect or ascending, 1.5-3 dm. tall, slender, branching from the base, pubescent : leaves 

 crowded ; blades oblong to oblong-lanceolate, 1.5-2.5 cm. long, obtuse or notched at the 

 apex, entire, glabrous or glabrate, short -petioled : flowers crowded in small axillary 

 clusters, monoecious : sepals delicate, about 2 mm. long, 3-nerved, narrowed into claws : 

 bracts about as long as the sepals : stamens 2 : utricle included, indehiscent : seeds 

 about 1 mm. long, shining. 



In valleys, Texas and adjacent Mexico. 



2. Amaranthus polygonoides L. Foliage bright green. Stems branched at the 

 base, the branches erect or spreading, 1-5 cm. long, often slightly pubescent : leaf-blades 

 rhombic, ovate or oval, 1-2 cm. long, obtuse or notched at the apex ; petioles longer than 

 the blades or shorter, slender : flowers monoecious, in dense axillary clusters : bracts 

 subulate : sepals (pistillate) about twice as long as the bracts, oblong-cuneate, with spread- 

 ing tips, apiculate, white-margined : utricle included, circumscissile : seeds barely 1 mm. 

 long. 



In sandy soil, Florida and the West Indies. 



3. Amaranthus GrSggii S. Wats. Foliage glabrous or nearly so. Stems erect, or 

 branched at the base, the branches ascending or spreading, 2-6 dm. long, commonly with 

 short branches : leaves few ; blades rhombic-ovate to oblong, 1-3 cm. long, thickish, 

 slightly scabrous, narrowed into short or slender petioles : spikes elongated, more or less 

 leafy-bracted, somewhat interrupted below : flowers dioecious : bracts- lanceolate, acumi- 

 nate, scarious : sepals much longer than^ the bracts, distinct, equal or nearly so, acute : 

 stigmas usually 3 : utricle indehiscent. 



In valleys, southern Texas near the mouth of the Rio Grande. 



4. Amaranthus Falmeri S. Wats. Foliage glabrous or nearly so. Stems erect, or 

 branched at the base, the branches ascending or decumbent, 2-9 dm. tall, leafy : leaf-blades 

 rhombic-oblong to rhombic-ovate, or almost lanceolate, 1.5-6 cm. long, obtuse or mu- 

 cronate ; petioles commonly as long as the blades : flowers dioecious : spikes conspicuously 

 elongated, interrupted below, often leafy at the base : bracts conspicuous, rigid, awn-tipped: 

 sepals much shorter than the bracts, nearly equal, commonly obtuse or retuse and apicu- 

 late : stigmas usually 2 : utricle indehiscent. 



In valleys, Texas to California, south to Mexico. 



5. Amaranthus Powellii S. Wats. Foliage sparingly pubescent or glabrate. Stems 

 erect, 4-7 dm. tall, sparingly branched : leaf-blades lanceolate to elliptic or ovate, 1.5-7 

 cm. long, obtuse or acutish, narrowed into short or slender petioles : flowers polygamous : 

 spikes 2.5-10 cm. long, or those in the axils shorter : bracts subulate, 3-4 mm. long, 

 rigid : sepals shorter than the bracts, 5, unequal, oblong, acute : stamens 3 : utricle about 

 as long as the calyx : seeds oblong-ovoid, fully 1 mm. long, shining. 



In valleys, Texas to Arizona and adjacent Mexico. 



6. Amaranthus retroflexus L. Foliage roughish pubescent, bright green. Stems 

 erect or ascending, 3-30 dm. tall, more or less branched, not spine-armed : leaf- blades 

 ovate to ovate-lanceolate, or lanceolate near top of stem, often conspicuously rhombic, 5-15 

 cm. long, undulate or crisped, cuneate at the base ; petioles shorter than the blades : spikes 

 dense, 1-6 cm. long, sessile : bracts subulate : sepals green, about \ as long as the bracts, 

 oblong or oblong-spatulate, mucronate, scarious : stamens 5 : utricle surpassed by the 

 sepals, wrinkled, circumscissile : seeds fully 1 mm. long. 



In waste places and fields, North America, except the extreme north. Naturalized from tropical 

 America. 



