DISPERSAL BY WIND. 



849 



Steppes of the East produce smooth, ellipsoidal fruits about the size of a hazel-nut 

 and so light that if one of them is laid on a person's open hand when his eyes are 

 shut he does not perceive its presence. The extraordinarily small weight of these 

 fruits is due to the fact that their structure includes a layer resembling the pith of 

 the Elder. A fruit of Cachrys alpina measures 13 mm. in length and 10 mm. in 

 thickness and weighs - 07 grm.; another Cachrys fruit from Shiraz is 15 mm. long 

 and 10 mm. thick and weighs only 0'06 grm. When fruits of this kind fall they 

 are rolled along over the Steppe by the wind and only come to rest when they are 

 caught in some crack in the parched clay soil or get lodged in a hole in a rock. A 

 few Papilionacea? also produce rolling fruits of the kind. One of the groups of 

 species belonging to the Medick genus, of which Medicago scutellata (see tig. 464 5 ) 

 may be taken as a type, has pods which are spirally curled into round balls and 

 which, when their seeds are ripe, detach themselves from their stalks and are rolled 



Fig. 465. Dispersion of fruits and seeds by the wind. Plantago Cretica. 



a little way along the ground every time there comes a gust of wind. The same 

 thincr happens inthe case of Blumenbachia Hieronymi, a native of South America, 

 belong to the family Loasacese. Although the spherical fruit of this plant has 

 a diameter of 2-5 cm. it only weighs 0'34 grm. when thoroughly dried. As soon a 

 the seed, are ripe the fruit-stalk withers and the round fruits, which are then 1, 

 lyincr loose upon the ground, are rolled away by the gentlest breeze. 

 iHTopped anywhere, and they get wetted by rain, ^*^*^% 

 formed in them become enlarged and a quantity of wrinkled seeds all out 

 Parwychia KapeUa (see fig. 468 ), a plant of wide distribution in the flo 

 the Black Sea, where it grows on dry rocky soil, bnngs small fruito to maturity , 

 he height of summer, each of which is surrounded by silvery white -embranous 

 bracts men the season for the dispersion of these fruits arrives the entire tuft of 

 which is in the form of a spherical glomerule, becomes detached from the 

 branch on which it grows and lies lightly on the ground, where the least puff of 



