WEEDS OP THE R VGWEED FAMILY 



L51 



State, occurring everywhere in both cultivated and pasture land. 



but especially abundant in stubble 

 fields after the crops have been har- 

 vested. July-Oct. Tin- slender ra- 

 cemes of little green starainate flow- 

 ers, like knots or beads along the 

 stem, produce a bounteous crop of 

 yellow pollen which thickly coats 

 the clothing of whoever passes 

 through a clump of ragweed on an 

 August day. Both it and the great 

 ragweed are known as "hay-fever 

 plants," their pollen spores when 

 inhaled being popularly supposed to 

 germinate in the nostrils and irri- 

 tate the nasal membranes of persons 

 subject to the disease. The seeds or 

 fruit are common in clover seed and 

 retain their vitality for years when 

 buried in the soil, springing up 

 wherever the land is plowed or after- 

 harvest when other plants are absent. Remedies: mowing or burn- 

 ing over stubble in September; 

 early fall plowing followed by disk 

 harrowing: use of clean seed: late 

 cultivation in hoed crops; sheep 

 grazing when the plants are voung. 

 A prairie form, the lanc^-leaved 

 ragweed (A. bideniata Michx.) oc- 

 curs frequently in the western 

 counties of the State. From the 

 common form it differs in having 

 the sterile heads sessile, not slmrt- 

 stalked, and in the leaves being 

 lance-shaped, sessile, with one or 

 two sharp teeth near the base. 



Fig. Ill 



1, a staminate flowe r 



(After Vasey.) 



116. XA.vmirv spinosum L. Spiny 



Cocklebur. Dagger Cockletrar. 



Burweed. (A. I. 1.) 



Stem erect, much branched, I-:? 



feet high; leaves lanceolate, pointed, 



usually lobed or cut-toothed, shining, 



Pig 111'. '/. mature plant; h, branch showing 

 spines and burs; c. bur; d, cross-section of bur 

 showing 2 seeds. (After Dewey.) 



