DISTRIBUTION OF WEEDS 25 



themselves mechanically to the active distributing agent, and 

 in the other are swallowed with the food and are ejected 

 uninjured after passing through the body of the animal. 



The fruits of agrimony (Fig. 10 A), wild carrot (Fig. 

 10 B), goosegrass (Fig. 10 C) and corn buttercup (Fig. 10 D 

 and Fig. li) are all provided with hooks of various types 

 which catch on to the wool or hair of animals that pass 



A 



FIG. 9. PLUMED SEEDS OF WILLOW-HERB (Epilobium s/.). 



A. Fruit split open, showing Seeds. 



B. Single Seed, natural size, showing Plume. 



C. Seeds, enlarged. 



amongst them, or on to the clothing of human beings. Shep- 

 herd's needle (Fig. 12) has less obvious hooks, but the fruits 

 are distinctly rough and are well able to cling. The bent 

 awn and numerous hairs of wild oat (Avena fatud) aid in its 

 distribution by animals, and it is possible that the hygroscopic 

 character of the awn, which twists and untwists according to 

 the dampness of the air, may also play a part in the spread of 

 this weed. 



