442 KINSHIP AND ADAPTATION 



often connected in some helpful way with the life of the in- 

 dividual — hairy appendages insuring to achenia widespread 

 dissemination by wind, and the power to climb facilitating 

 economically the quick exposure of green parts to sunlight. 

 In such ways an organism, as we have seen, is adjusted, 

 often marvelously well, to its environment; and we call the 

 adjustments which promote its welfare adaptations. It is 

 with questions of the origin and inheritance of adaptations 

 that the debates of evolutionists are mainl}^ concerned. We 

 must, therefore, at the outset examine carefulh' just what is 

 meant by an adaptation. 



Every individual plant or animal is found to have the 

 power of modifying its form or behavior in response to out- 

 side influences, and such modification is often beneficial. 

 Indeed we need not distinguish here between form and 

 behavior, for even structure is but the result of growing in 

 certain ways, and growth is merely a slow kind of behavior. 

 So we may say that each living thing, in so far as it is alive, 

 has a certain limited power of adaptation through direct 

 response to environing influences. As a seed sprouts, its 

 little root turns toward the place of greatest moisture, while 

 the young leaves are directed toward the light, and if the 

 illumination be feeble the stem helps the leaves by elongating 

 more than it would if the light were stronger. A tree exposed 

 to strong winds of one prevailing direction takes on a one- 

 sided form thereby reducing the strain. Herbs which in 

 rich moist soil produce tall stems and ample foliage before 

 they flower, will on a sandy roadside bloom as soon as they 

 have made a few small crowded leaves and are only a few 

 inches high, thus, doing the best they can under adverse 

 conditions. Dandelions grown on a mountain side look very 

 different from those grown in the lowlands (Fig. 301), and 

 the peculiarities of each seem to fit in especially well with the 

 contrasting conditions. Such cases of advantageous adjust- 

 ment made during the life of an organism may be termed 

 individual adaptations. From these we must distinguish 

 characteristic adaptations, or advantageous peculiarities be- 

 longing to whole groups. Of such adaptations the charac- 

 teristics of clematis above referred to may serve as examples; 



