494 



WEED FLORA OP IOWA 





^. 



Fio. 371. Seeds of Burdock (.Arotimm, lappa), a, a side view of one of the Inner 

 achenes of a bur; b, showing the Inner surface of a curved, outer achene, 

 and exhibiting the character of the apex, both enlarged; c, a group show- 

 ing natural size. 



(After Hlllman, BuU. Nev. Agr. Exp. Sta.) 



Tall Thistle {Cirsimn altissirmum, Willd.). 



Achenes lanceolate-obovate, tapering toward lower end, and some- 

 what narrowed toward the apex, wider in the middle, one-eighth in. 

 in length ; width one-twelfth in. ; duU brown or grayish excepting 

 light colored ring at upper end; numerous fine ridges; apex con- 

 cave, with the remnant of corolla tube projecting from the center; 

 color uniform; not marked by light and dark areas as the bull 

 thistle. 



Fig. 372. 



v.liat tl 



sli.-ipi'rl 



I'lirvcil 

 V. i;li :i 

 sued ol' 



Pig. 372A 



Seeds of Thistles. A. Different views of Canada Thistle ICiraium 

 arveme). B. BuU Thistle {Ciraium, lanceolatum') . 

 (Drawings by Charlotte M. King.) 



Cacada Thistle {Cirsium arvense (L.) Scop.). 



•v.r I.-niM" I Vio, inricv.pil r.t lower pnrl. tapering from some- 

 lii Icind U.,-\ oi'c-tv, cirik to ()i:c-fi.'l.;!i i-i. Iniii:: i!ii- i-i;i- 



lop witli a ],rc}ifctw'4 (■(•!:!•.• I |ri)-li-i;. sliriirlit n-- s!i}:litly 

 : r;!;ii''c^'(l willi It ngiliulinal (iiiik li"is m- r;:;Tci\vs ; -mi-k 

 li'jlit 'olii.'id b(ir''r'r. giving' apicr'r; n; c oT a ring. I'ouihI in 



sin:;!! g!-ai!:3, clovers am'. y;;;£st.'s. 



