DISPERSAL OF WEED SEEDS 



21 



west of Ames averaged 53 vigorous specimens of rib- 

 grass. Two areas 12 feet square upon a farm near Mar- 



Fig. 15. Burdock head with many "seeds" scattered by animals. 

 (Dewey, U. S. Dept. Agrl.) 



Fig. 1 6. "Seed" of pitchforks, Spanish needle, scattered by animals. 

 (U. S. Dept. Agrl.) 



athon averaged six ribgrass and three wild carrot plants. 

 In another piece of the same field not cut at Marathon, 



Fig. 17. Seeds scattered by explosive properties. A, geranium; B, 

 wood sorrel; C, pod or common vetch. (U. S. Dept. Agrl.) 



