448 



cial adaptaticin of the plant to its insect visitants — no lure to insects ca- 

 pable of service to it or special apparatus of defense against those able to 

 injure it. The fertilization of its seed is fully provided for without ref- 

 erence to the agency of insects. It has no armature of spines or bristly 

 hairs to embarrass their movements over its surface or to defend against 

 their attack its softer and more succulent foliage. It secretes no viscid 

 fluids to entangle them and forms no chemical poisons or distasteful com- 

 pounds in its tissues to destroy or to repel them. The cuticle of its leaf 

 is neither hardened nor thickened by special deposits ; its anthers are 

 neither protected nor concealed ; and its delicate styles are as fully ex- 

 posed as if they were the least essential of its organs. Minute sucking 

 insects are able at all times to pierce its roots and its leaves with their 

 flexible beaks, and, with the single exception of its fruit, there is no part 

 of it which is not freely accessible at any time to any hungry enemy. Only 

 the kernel, which is supposed to have been lightly covered in the wild 

 corn plant by a single chafi^y scale or glume, has become in the long course 

 of development securely inclosed beneath a thick coat of husks, impene- 

 trable by nearly all insects; and we may perhaps reasonably infer that, 

 among the possible injuries against which this conspicuous protective 

 ^tructure defends the soft young kernel, those of insects are to be taken 

 into account. 



There are, of course, many insect species, even among those which 

 habitually frequent the plant, which are unable to appropriate certain 

 parts of its substance to their use, but this is because of the absence of 

 adaptation on their part and not because of any special defensive adapta- 

 tion on the side of the plant. Thus we may say that, with the exception 

 of the ear, the whole plant lies open and free to insect depredation, and 

 that it is able to maintain itself in the midst of its entomological depend- 

 ents only by virtue of its unusual power of vigorous, rapid and super- 

 abundant growth. Like every other plant which is normally subject to a 

 regular drain upon its substance from insect injury, it must grow a sur- 

 plus necessary for no other purpose than to appease its enemies ; and this, 

 in a favorable season, the corn plant does with an energltic profusion un- 

 exampled among our cultivated plants. Insects, indeed, grow rapidly as 

 a rule, and most of them soon reach their full size. Many species mul- 

 tiply with great rapidity, but even these the corn plant will outgrow if 

 given a fair chance, provided they are limited to corn itself for food. 



Turning to the other side of the relationship, we may say that the 

 corn insects exhibit no structural adaptations to their life on the corn 

 plant — no structures, that is to say, which fit them any better to live and 

 feed on corn than on any one of many other kinds of vegetation. This 

 was, of course, to be expected of the great list of insects which find in 

 corn only one element of a various food, and that not necessarily the most 

 important; but it seems equally true of those which, like the corn root- 

 worm or the corn root-aphis, live on it by strong preference, if not by 

 absolute necessity. 



