ON FRUITS AND SEEDS. 



169 



similar manner, there are differences which might not at first be sus- 

 pected. Thus in some cases, as, for instance, the pine, it is the seed 

 itself which is winged ; in Thlaspi arvense it is the pod ; in Entada^ 

 a leguminous plant, the pod breaks up into segments, each of which is 



Fig. 12. a, maple; 6, sycamore ; c, lime ; <Z, hornbeam ; ^, elm ; /, birch ; g^ pine; A, fir ; i, ash. 



winged ; in Nissolia the extremity of the pod is expanded into a flat- 

 tened wing ; lastly, in the lime, as already mentioned, the fruits drop 

 off in a bunch, and the leaf at the base of the common flower-stalk, or 

 " bract," as it is called, forms the wing. 



In Gouania retinaria of Rodriguez the same object is effected in 

 another manner ; the cellular tissue of the fruit crumbles and breaks 

 away, leaving only the vascular tissue, which thus forms a net inclos- 

 ing the seed. 



Another mode, which is frequently adopted, is the development of 

 long hairs. Sometimes, as in Clematis, Anemone, Dryas, these hairs 

 take the form of a long, feathery awn. In others the hairs form a tuft 



