1. Amaranthus L. Pigweed. Amaranth 



Annual weedy herbs, especially near irrigated or cultivated places, monoecious 

 or dioecious; stems erect or prostrate, branching at the base or above; leaves alter- 

 nate, petiolate, flat, pinnately veined, entire or undulate; flowers unisexual or a 

 few appearing perfect, with staminate and pistillate flowers on the same or sepa- 

 rate plants, in dense terminal or axillary spikes or clusters, each subtended by 3 

 conspicuous red, green or purple bracts; perianth segments (tepals) 2 to 5 (only 

 1 evident in A. calif ornicus) , distinct, glabrous; stamens 5, sometimes 1 to 3, 

 separate; anthers 4-celled (appearing 2-celled after dehiscence), opening lengthwise, 

 the filaments distinct; ovary 1 -celled, with 2 or 3 stigmas; ovule 1; utricle one- 

 seeded, 2- or 3-beaked at the apex, circumscissile. irregularly splitting or inde- 

 hiscent; seeds lenticular, erect, compressed, lustrous, smooth; embryo coiled into a 

 ring around the albumen; radicle inferior. 



About 60 species, cosmopolitan. 



Because of their tremendous production of seeds that may be carried over into 

 the winter, the pigweeds are a vital source of food for songbirds, game birds and 

 other species of wildlife. 



1. Flowers all or mostly in small axillary clusters (2) 



1 . Flowers mostly in elongate terminal spikes or compound panicles, much smaller 



panicles or clusters may also be present (4) 



2(1). Utricle indehiscent; seeds obovate 1. A. crassipes. 



2. Utricle circumscissile at the middle (3) 



3(2). Tepals of pistillate flowers 1 to 3. all except one reduced to minute scales 

 or wanting; stems slender, prostrate, forming mats; seeds orbicular.. 

 2. A. calif ornicus. 



3. Tepals of pistillate flowers 3, equal or nearly so; stems stout, erect or ascend- 



ing; seeds lenticular 3. A. albus. 



4(1). Spines present in the axils of the leaves; utricle irregularly or imperfectly 



dehiscent; plants monoecious, occasional flowers perfect 



4. A. spinosus. 



4. Spines lacking; utricle regularly cricumscissile; plants dioecious; flowers all 



staminate or all pistillate (5) 



5(4). Outer tepals (at least the largest) acute to acuminate with the midvein 

 excurrent as a rigid point; bracts and outer tepals conspicuously 

 longer than the inner tepals 5. A. Palmeri. 



5. Outer tepals obtuse to retuse or sometimes acute, apiculate but the dark vein 



not excurrent; bracts and outer tepals shorter than or scarcely 

 exceeding the inner tepals 6. A. arenicola. 



1. Amaranthus crassipes Schlecht. Fig. 425. 



Plant from an elongate taproot; stems prostrate or decumbent, 2-6 dm. long, 

 often sparingly branched, rather fleshy, glabrous; leaves alternate, with petioles 

 4-40 mm. long, obovate to elliptic, 1-4 cm. long, round or notched at the apex, 

 cuneate at the base, deep-green, glabrate; inflorescences axillary, the short axes 

 much-thickened (to 1 mm.) and indurate; male and female flowers on same plant 

 or occasional flowers appearing perfect; bracts minute, keeled; tepals of the pistil- 

 late flowers 4 or 5, spatulate, scarious, 0.2-2.5 mm. long; style bifid or trifid to 

 the base; utricle compressed-obovoid, 1.4-1.8 mm. long, obtuse or emarginate, 

 papillate above the middle, coriaceous, indehiscent; seed broadly obovate, 1-1.4 

 mm. long, dark-brown or black, lustrous. A. Warnockii I. M. Johnst. 



On mud and gravel bars in rivers, along creeks and in playa lakes, in Tex. from 

 the coast through the Rio Grande Plains and Edwards Plateau to the Trans-Pecos, 

 June-Oct.; nat. of trop Am.; naturalized in waste places along the Gulf Coast and 



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