SITNGENESIA NECE3SARIA. 479 



1. StRUMARIUx^. 



X. caule ineimi, ra- I Stem unarmed, 

 moso; foliis cordatis, branching; leaves cor- 

 lobatis, serratis, sea- date, lobed, serrate, 

 bris, irinervibus; frue- scabrous, three-nerved: 

 tibus ellipticis, piibes- fruit elliptic, pubescent, 

 centibus, setis rigidis armed with rigid hook- 

 uncinatis. | ed bristles. 



r 



Sp. pi. 4- p. 373. Mich. 2. p. 182. Pursh, 2. p. 581. Nutt- 2. p. 186. 

 A- Amencanum^ Walt. p. 231. 



Plant annual. Stem three to six feet high, branching, angled, pubescent 

 and very scabrous. Leaves alternate, generally three-lobed, the lobes 

 coarsely toothed, pubescent and very scabrous on both surfaces, six to eight 

 mches long, nearly of the same width, on petioles three to four inches long 

 iieads of mahjlorets arranged on axillary racemes. Leaves of the involu- 

 cruni subulate. Stamens united at base. Anthers distinct. Chaff of the 

 receptacle subulate. Fertile forets one or two at the base of each raceme. 

 Involucrum ten-leaved, two-flowered, the leaflets subulate, equal. Proper 

 cafyx an arillus? oblong, armed with hooked prickles of which the two at the 

 summit become much larger than the others. Seed oblong, inclosed in the 

 persistent calyx. 



The germs in this plant which when young appear to be distinct, unite as 

 they mature and form a two-celled bipartible? fruit. 

 Grows in fields and about buildings— very common but not indigenous. 

 Flowers July— October. Sheep-bur. 



2. Spinosum. 



X. spinis ternatis;! Spines ternate; leaves 

 lohis trilobis. I three-lobed. 



n 



Sp, pi. 4. p. 374. Nutt. 2. p. 186. 



Annual. Stem three to five feet high, terete, pubescent. Leaves aher- 

 Da P ^'^'^^^-'^n^^eolate, acute, when young entire, when old, three-lobed, 

 P e green, pubescent on the upper surface, almost tomentose underneath. 



lon^ *""** *** ^^"^^^ ^^"^^ ^°"^' ^ ^P'"^ three-forked, rigid, about an inch 

 axilla ^'■^*V\«°e side of each petiole. Heads of male forets solitary, 

 ary at the base of each spine. Involucnim many leaved; leaves ovate. 

 titeT longer than the corolla, united at base. Jnthera distinct. Fer- 

 ahnllT^^f ^^"'^'T' axillary, opposite the spine. Proper cahx armed with 

 «ort hooked prickles. Stales two. Fruit two-cellei 



An 



and 



