THE GENERAl. CHARACTERS OF SEEDS 



483 





Fig. 356A Fig. 356B 



FiQ. 356. Seeds of Small Ragweed and Cup Plant. A. Single achene of Cup 

 Plant (.Silphium perfoUatum). 



B. Achenes, various views of Small Ragweed (.Ambrosia artemisiaefoUa) ; A, 

 five specimens having the outer covering, and showing the crown of teeth, 

 or spines ; B, one having the covering partially broken away, exposing the 

 achene ; C, aohene, the covering persisting only at the base ; D, a sectional 

 view of a fruit; E, a group showing the natural size. 



(A, drawing by Ada Hayden; B, after- HlUman, Bull. Nev. Agr. EScp. Sta.) 



involucre reticulated, somewliat brittle, achene with thick, rather 

 hard wall ; cotyledons 5, large, thick, fleshy, oily ; eaulicle short. 

 In clovers and alfalfa. 



Liance-leaved Ragweed {Ambrosia hidentata Miehx.). 

 Involucre top-shaped (turbinate) , closed, yellowish or brownish ; 

 length, exclusive of the spine, one-tenth to one-eighth in. ; 1 very 

 prominent lobe and .6 or more prominent tubercles; surface of in- 

 volucre rough and. hispid, pubescent. 



Fig. 357A Fig. 357B Fig. 3570 



Fig. 357. Seeds of some Ragweeds. A. Ambrosia bidentata. B. Ambrosia 



psilostachya. C. Ambrosia trifida. 

 (Drawings, A, Charlotte M. King ; B, Ada Hayden ; C, after Hillman. Bull. 



Mich. Exp. sta.) 



