FRUITS AND COLONISATION BY SEED. 43 



5. Elastic or explosive movements of some part of the 

 fruit or seeds throw the seed some distance from the 

 parent plant. 



There are two kinds of simple fruits ; those in which 

 the fruit opens so that it is the seed that is free to 

 travel to a new position (the dehiscent forms) and the 

 indehiscent^ in which the entire fruit (with the contained 

 seeds) is carried away either by wind or by some one 

 of the other agents already named. Very often seeds 

 and fruits show almost exactly the same modifications. 



Of the forms with hairs or hooks the common Goose- 

 grass or Robin-Eun-the-Hedge {Galium apajine) is an 

 excellent example ; the fruit, which consists of two 

 carpels, is entirely covered with small and very tena- 

 cious hairs. These cling very closely to cloth, or to an 

 animal's coat, and may be carried many miles before 

 they break and the seeds escape. 



Similar, usually hooked, clinging hairs are found on 

 the fruit of Sanicle, of Chacrophyllum Anthrisciis, 

 and of a few other Umbelliferae. The sepals of most 

 species of Forget-me-not and of the Agrimony {Agri- 

 monia Eupatoria^, as well as the fruits of Cynoglossum, 

 are covered with hairs which act in the same way. In 

 the genus Medicago (one of the Legtiminosae) the pod, 

 instead of being straight, is coiled into a spiral ; 

 generally along the edge of this spiral are small stout 

 spines, sometimes curving over, or in other cases 

 diverging in different directions. These pods are very 

 common in sheep's wool, and it is very difficult to get 

 rid of them until the pod decays and permits the seed 

 to escape. 



The Burdock {ArctiiLm majus) is particularly interest- 

 ing, as whole heads of flowers become attached to the 

 fleece of sheep or other animals. In this case each of 



