368 CLASS XXI. ORDER V. 



380. AMBROSIA. 

 Ambrosia elatior. L. Tall Ambrosia. RomanWormwood. 

 Leaves twice pinnatifid, smoothish, petioles ciliated ; 

 racemes terminal, panicled ; stem wandlike. Willd. 



A troublesome weed in cultivated grounds, hardly entitled to 

 the character which its name might imply. Stem erect, branch- 

 ing, from one to three feet high. Leaves bipinnatifid, the upper 

 ones pinnatifid, with parallel segments gradually decreasing in 

 length toward the point. Barren flowers nodding, small, in ter- 

 minal racemes. Fertile flowers lower down, sessile about the 

 axils of the upper leaves. — August, September. — Annual. 

 Ambrosia trifida. L. Giant Ambrosia. 



Hairy, rough : leaves three lobed, serrate, the lobes 

 oval-lanceolate, acuminate ; fruit with six spines be- 

 low the lip. 



Much larger in all its parts than the preceding, and sometimes 

 six or seven feet high. — On the banks of Connecticut river, 

 Northampton. — August. — Annual. 



381. AMARANTHUS. 

 Amaranthus hybridus. L. Hybrid Amaranth. 



Racemes pentandrous, decompound, crowded, erect; 

 leaves ovate-lanceolate. Willd. 



This is a common weed in waste and cultivated grounds. 

 Stem erect, furrowed, somewhat hairy. Leaves alternate, on 

 long petioles, green, ovate, mostly entire, mucronated, the lower 

 ones retuse at the end. The flowers are crowded, small, and 

 obscure, forming large, green clusters, axillary and terminal, 

 which turn to a dull red as the plant grows old. — Annual. 



Amaranthus blitum. Willd. Low Amaranth. 



Racemes triandrous, somewhat spiked ; flowers 

 three leaved ; leaves ovate, retuse; stem spreading. 



Found in the same places as the last. A smaller plant, 

 spreading or prostrate. — July.- 



