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 character are least liable to be destroyed. 
Fig. 7. Three Seeds of Castor Beans, Brown and Mottled, not easily found when thrown on the Ground. (Slightly enlarged.) By a process of selection for many generations, no doubt, seeds have acquired their present colors, and some of them are still undergoing 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 produces beans more or less approaching a sphere in shape.[1] 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
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 complete 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.
