DISPERSAL BY ANIMALS. 



875 



the fruits developed upon it. Again, in Speculana falcata, Valerianella echinata, 

 Cornucopia cucullata, and Geratocephalus falcatus (see fig. 478'*) the fruits do not 

 sever themselves from the stems when their claws become attached to animals, but 

 the entire plant is upi'ooted and carried away. A similar phenomenon is observed 

 when a fruiting plant of Setaria verticillata is touched by one of the larger birds 

 or some other animal. The fruits of this Grass are wrapped in awnless glumes 

 and surrounded by involucral bristles furnished with very sharp barbs (see figs. 

 477 '* and 477 '''). When the bristles get fastened to an animal, not only the fruiting 

 spike, but often a piece of the haulm as well, is dragged away, and sometimes the 

 entire plant is uprooted and taken off. Such fortuitous appendages are very 

 troublesome to the animal, and are got rid of as soon as possible. In many instances 

 this is achieved without great difficulty by rubbing the coat against fixed objects, 

 or by using the feet, snout, or beak, as the case may be, to disembarrass the body. 

 Sometimes, however, the sharp claws and barbs of the fruits are so firmly imbedded 



..-,X 



■ r-^ ■'■■'■ 





'l^:::'-';";;x: 





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Pig. 4S0. -i'ruitä with iivt'dlc-IikL- spines. 

 1 Pedalium Murcx. 3 Tribulus orietiialis. 



or entangled in the hair or feathers that their extrication is attended with much 

 difficulty and suffering. 



A mode of fruit-dispersion involving still greater pain to animals is that which is 

 accomplished by means of straight, smooth prickles projecting from the fruit, and so 

 situated as either to bore into the foot of any animal that treads upon it, or to stick 

 into the coat of one that merely brushes by. Two groups of these fruits may be distin- 

 guished. The first group comprises those which lie loose upon the ground when they 

 are ripe. To it belong Acicarpha, Ceratocarpus, Salsola, and Spinacia, in which the 

 tips of the fruiting calyx liarden and are transformed into spines standing straight 

 up, and also Rogeria, Pedalium, and Tribulus (see figs. 480 ' and 480 "), in which 

 the spines project from the fruit-walls. One of the species of the last-named genus, 

 viz., Tribulus orientalis, is of common occurrence in the lowlands of Hungary, and 

 is an object of dread to the shepherds of that region. The fallen segments into 

 which the fruit resolves itself are armed with hard, sharp, comparatively long 

 spines, and are often so covered with drifted sand that only the tips of the spines 

 project above the surface (see fig. 480 ^). These prickles pierce deep into the hoofs 

 and soles of animals that tread upon them, and are broken off the fi-uit by the 

 eflbrts of the latter to rid themselves of the impedin>ent. They are thus left sticking 

 in the skin, and cause very painful, festering wounds. As examples of the second 

 gi'oup of fruits furnished with sharp prickles as instruments of dissemination we 



