DISPERSAL BY ANIMALS. 



873 



being eaten. Rogeria and Pedalium, mentioned on p. 875, also belong to this 

 family. 



In other plants it is the fruit-stalk instead of the style which is transformed 

 into a claw-like structure. In Cyclamen Europoium, for instance, the fruit-stalk 

 undergoes spiral torsion and contraction. Formerly it was supposed that the object 

 of this curious phenomenon was to draw the fruits into the earth, where the seeds 

 would be favourably situated for germination. But this idea does not correspond 

 to actual fact. The green capsules are drawn underground in the late autumn 



Fig. 478.— Fruits with hooks. 

 1 Marruhium vulgare. 2 Medicago agrestis. s Jtumex nepalerms. * Scorpiurus sulcata. • Agrimonia odoiata. * Orlaya 

 grandijlora. 7 Pteranthus echinatus. > Rochelia Persica. » Onobrychis cequidcntata. to Trium/etta Plumien. n Uookcd 

 bristles on the fruit of Trium/etta Plumieri magnified. ^ Medicago radiata. '« Xanthium spiuvturn, »« Ceratocephalus 

 falcatus. 15 Geum urbanum. '« A single fallen fruit of Geum urbanum. if Lappa major. 



when the seeds are still unripe. They pass the winter in the earth, and do not 

 attain to complete maturity until the following summer. The desiccation and 

 severance of the twisted fruit-stalk then has the efiect of pulling tiie fruit out of 

 the ground again, the lower portion of the stalk rots, and the part which is left 

 forms a claw surmounting the capsule. The latter, which is still full of seeds, lies 

 loose on the ground, and adheres to the foot of any animal that treads on it. The 

 manner in which these seeds are besides dispersed by ants has already been referred 

 to on p. 866. 



