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AMERICAN HOMES AND GARDENS 



September, 1906 



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Tent Caterpillar Traveling Up the Trunk of a Tree 



Earth-Cone Trap Showing Tussock Larvae 



enough to resist, say when about half-grown, when the pest which are believed to be its natural enemy and by the aid 



leaves it and begins on the leaves and continuing until the of these parasites hope to complete the extermination of 



tree is completely defoliated. the tussock, not discontinuing the methods heretofore em- 



Since the tussock moth successfully resists all solutions ployed to reduce its numbers, 

 composed of arsenic, the entomologists have abandoned this Full grown the female tussock moth measures one and a 



method of attack and are cultivating certain flies and wasps quarter inches in length. 



Plant Sensation 



|NE of the most recent discoveries gives such 

 a deep insight into the strangeness and (ac- 

 cording to our other ideas) foreignness with 

 which the life of plants expresses itself, that 

 it must be of greatest interest to the widest 

 circles. This is the form-perfection (mor- 

 phaesthesia) of plants. This strange name the Berlin botan- 

 ist, Professor Roll, inflicted recently upon the fact discovered 

 by him, that the position of their organs exerts a stimulus 

 upon plants. In experiments with sprouts and young speci- 

 mens of the most varied food-plants, he noticed that on their 

 vertical or bow-shaped principal root the little side roots are 

 always so arranged that they stand only on the convex side 

 of the curvature. This strange behavior can be no accident, 

 for it is found throughout their distribution among all ex- 

 amined plants — ferns as well as trees and shrubs. The lay- 

 man would probably find in this behavior only an interesting 

 fact; the botanist was forced to say to himself that a phe- 

 nomenon of such universal scope could only be the expression 

 of a special obedience to law. Roll investigated it also in 

 experimental ways, and forced roots into certain artificial 

 curvatures, with such success that the new-forming little side 

 roots formed themselves again only on the outward-curved 

 side of the principal root. 



It thus appeared that the organs of plants are bound to a 

 quite fixed mutual position; and this, all at once, sheds light 

 upon many relations hitherto enigmatical. It had long been 

 noticed that all plants have an appearance highly character- 

 istic of them and exactly determined — i. e., brought about 

 by the fact that, in all variability of size, of leaf-forms of 

 exuberance in the development yet the mutual place of the 



branches, leaves and blossoms is fixed with perfect regularity 

 — somewhat as different buildings are obliged to correspond 

 with each other, w T hen they are built in the same style. This 

 was called the habit of plants. It is unconsciously familiar to 

 every one schooled in nature, for this habit it is by which 

 from a distance the woodsman can distinguish, e. g., the fir 

 tree from the pine tree so like it. By the most varied con- 

 siderations (the discussion of which here would lead too far) , 

 attention now came to be given to the question of the single 

 factor by which this habit is governed; and it was found that 

 it is caused, first and foremost, by the arrangement of the 

 side limbs, branches, twigs, leaves, which for every plant 

 produce a mathematically constant type. Within this type, 

 then, the individual variation creates the differences between 

 the single-plant individuals, which otherwise would have to 

 resemble each other as one egg another. This individual 

 variation, however, depends upon the nourishment condi- 

 tions and the fitness of the individual for its special life con- 

 ditions. That was a very significant discovery, which first 

 makes the special life of plants comprehensible to us. They 

 possess the capacity in the most wonderful fashion always to 

 make the most of the given circumstances and adapt them- 

 selves to them so as to reach the normal life conditions. The 

 best witness thereto is their habitat. 



As this capacity was investigated, the most incredible 

 proofs were reached with what exquisite adaptation to plan 

 the forces of Nature act. For example, the leaves of plants 

 stand in a fixed order, so that all may share the sunlight. 

 This is the case even with the thicket-foliaged treetop. This 

 explains why in the growth of twigs and branches there is 

 here no hindrance by foliage and branches. 



