lOi. TIIK AMERICAN iMONTlILV | April, 



the tlij^cstivf action wlicn swallowril l)y birds; and (</) of a dull, 

 brownish color and minutely furrowed surface presentinij a re- 

 luarkahly sandy aspect wiien seen without the microscope. 



What is the sijjnilicance and the cause of evolution of these last 

 features, which constitute the principal microscopical peculiarities 

 of the specimen? Apparently they must be related to the<lissem- 

 inatiun Iw ajjency of birds, anil in this respect they may be im- 

 portant in either one of two exactly opposite wavs. The obscure 

 and siindy appearance wouKl evidently render it ditficult for the 

 hirtis to find ami carry otVthe seeds sufficiently to prevent crowd- 

 injj in the immediate neijjhborliood ; anil this mav account for the 

 h.iW\t of the plant to overst<Jck, to an exceptional de«^ree, fields in 

 which it has become established. On the other iiand. thev seem 

 adapted to bird-dissemination to a moderate dei^ree ; anil the ex- 

 tent to which this actuallv occurs ami is of service to the species 

 is an interesting; question for future investij^^ation. 



Fruits that are highly specialized for binl-dissemination, such 

 as most of the familiar berries. are large enough to be easily found 

 and to be worth the trouble of eating, and are of showy colors, 

 red. which seems specially attractive to birds anil to some other 

 fruit-eating animals, blue, blackish, or white. A few hanilsome 

 and showv seeds appeal likewise to the vision of the birds ; but 

 being hard and probably not digestible they have been considered 

 unserviceable to the birds, and attractive only to young and inex- 

 pcrienceil ones that had not yet learned their uselessness, and that 

 are, therefore, by misapplying the teachings of instinct that attrac- 

 tive-looking fruits are good to eat. easily duped into taking and 

 swallowing what will prove useless to them. But is there any 

 proof of this in the known facts, and is it probable that the instinct 

 of the birds would be thus misled sufficiently to cause the high 

 degree of specialization already attained in such seeds .^ I think 

 not. It seems far more likelv that the birds, not misguided, hut 

 led by a true instinct, swallow these hard morsels not as food, nor 

 in vain, but as mechanical aids to digestion, as birds are known to 

 do in some cases, having learned bv experience that the nourish- 

 ing food serves them better in such company. This theory would 

 account for the swallowing of these indigestible morsels, even 

 when, as in the present case, they do not look like edible berries, 

 and also for the evolution, as vet unexplained, of the granular- 

 looking surfaces variouslv wrinkled, furrowed, honeycombed, 

 pitted, tubercled. or spiny, that ornament many kinds of minute 

 seeds and make them favorite microscopic objects. In case of 

 tiny birds, at least, the minutely-roughened surface would add 

 perceptibly to the value of these insoluble particles as triturantsor 

 local irritants, while the scidpturing of the surface may even assist 

 somewhat in finding and recognizing the oljjects. These iletails 

 are probablv more visible to a bird closely searching for food than 

 to our more distant view, since the size of the retinal image would 

 increase rapidly with the nearness of the eye to the object. 



