AMARANTHACEAE 83 



Spikes slender. 2. A. hyhridus. 



Flowers dioecious. 6. A. Pnlmeri. 



Leaves with two spines in axils. 3. A. spinosus. 

 Flowers in small axillary clusters. 



Plant prostrate-spreading. 4. A.hlitnides. 



Plant erect-ascending. 5. A. graecizans. 



1. A. retroflexua L. Kough Pigweed. 1°-10° high, ronghish-pu- 

 berulent: leaves ovate, entire or undulate, long-petioled : flowers greenish, 

 in dense terminal and axillary spikes : spikes ovoid-cylindric, compound 

 and often densely clustered : bracts awn-pointed : utricle circumscissile. 

 — A common weed in waste places. July-October. 



2. A. hybridus L. Slender Pigweed. Like the last but spikes 

 linear-cylindric, somewhat narrower, flexuous and not densely clustered. 

 — Also abundant in waste places. July-October. 



Var. paniculatus (L. ) Uline & Bray. Flowers and leaves tinged with 

 red. — Well distributed in waste places but not common. July-October. 



3. A. spinosus L. Spiny Pigweed. Bushy-branched, l°-4° high : 

 leaves rhombic-lanceolate, long-petioled, with a pair of stout spines in 

 their axils : flowers monoecious : spikes long and slender : utricle im- 

 perfectly circumscissile. — In waste jjlaces. Eather common. June-Octo- 

 ber. 



4. A. blitoides S. Wats. Creeping Pigweed. Widely prostrate- 

 spreading : leaves spatulate, petioled : flower clusters small : bract short, 

 acuminate : utricle circumscissile. — Abundant in waste places. June- 

 October. 



5. A. graecizans L. Tumble Weed. Resembles the last, but erect- 

 spreading : bracts subulate, rigid, pungent-pointed. — Frequent in waste 

 places throughout. June-October. 



6. A. Palmeri S. Wats. 2°-5° high, puberulent above : leaves ovate- 

 lanceolate, blunt at the apex, long-petioled : flowers dioecious, borre in 

 slender spikes : bracts subulate, spiny-awned : utricle indehiscent. — 

 Rarely adventized along railroad at Wayne City. Also at Argentine, 

 Kansas. August-October. 



2. ACNIDA L. 



Closely resembles Amaraufhus, save that the calyx is absent in the pis- 

 tillate flowers. Platits dioecious. 



1. A. tamariscina ( Nutt. ) Wood. Water Hemp. 6^-10° high : 

 erect to postrate-spreading, usually much-branched : leaves ovate-lanceo- 

 late, long-petioled : flowers in long spikes and in axillary clusters : utricle 

 circumscissile, usually somewhat angled and tubercled, membranous. — 

 Abundant in low grounds especially on sand-bars along the Missouri 

 River. June-November. Very variable. 



Var. tuberculata (Moq.) Uline & Bray. Tall and erect with spicate 

 inflorescence and a tubercled, indehiscent utricle. — Frequent with the 

 type. 



