PLANTS THAT HIDE FROM ANIMALS. 



183 



Seeds that mimic Pebbles. — Seeds are frequently met with that 

 are mottled or striped or of an inconspicuous color difficult to find 

 when dropped on the soil or among small pebbles. Seeds of this char- 

 acter are least liable to be destroyed. By 

 a process of selection for many generations, 

 no doubt, seeds have acquired their present 

 colors, and some of them are still under- 

 going this process. 



Certain sorts of cow peas resemble the 

 red soil found in some regions. Caster- 

 oil beans have been mentioned as examples 

 of those which are mottled. Some of the 

 cacti have an irregular shape and a dull gray color much resembling 

 stones of the desert. 



On the coast of some of the Philippine Islands, a coarse briar pro- 

 duces beans more or less approaching a sphere in shape.* They are 

 about the size of the finger tips of a man and some of them, like peas 

 crowded in the pod, have two flat surfaces. The color varies from 

 moderately dark to light drab, some giving a faint greenish tinge, while 

 the luster of many is exactly that of chert pebbles. Nearly all the 

 specimens show a series of approximately parallel darker lines passing 

 around, very suggestive of stratification. All are quite hard, cut only 



Fig. 7. Three Seeds of Castor 

 Beans, Brown and Mottled, not 

 easily found when thrown on 

 the Ground. (Slightly enlarged.) 



Fig. 8. Representing Four Seeds which closely resemble Pebbles, among which they 



were accidentally gathered. 



with difficulty with a knife, and when shaken together in the hand give 

 that clinking sound, only somewhat duller, which is characteristic 

 of pebbles. The mimicry then is that of mixed quartz pebbles, and 

 covers shape, size, luster, hardness and stratification. It is so com- 

 plete and perfect that it can not be regarded as mere coincidence 

 Placed in water, the beans are found to be buoyant. Undoubtedly this 

 mimicry of pebbles has saved many a seed from destruction by fish, 

 bird or reptile. 



* W. H. Sherzer, Bot. Gaz., Vol. XXI. 



