442 KINSHIP AND ADAPTATION 



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

 (_[ividual — hairy appendages insuring to achenia widespread 

 dissemination Ijy wind, and tlie power to climb facilitating 

 economicallj- the ((uick exposure of green parts to sunlight. 

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

 often niarvelousl\' 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 e\'olutionists are mainly concerned. We 

 must, therefore, at the outset examine carefully just what is 

 meant by an adaptaticjn. 



■ 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 l)eneficial. 

 Indeed we need not tlistinguish here l)etwe(>n form and 

 l)eliavior, 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 adajotation through direct 

 response to environing influences. As a seed s]:(routs, its 

 little root turns t(jward the place of greatest moisture, while 

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

 illumination l)e 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 flowei-, will on a sandy roadside bloom as soon as they 

 have made a few small crowded lea\'es and are only a few 

 inches high, thus, doing th(> best they can under atlverse 

 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 

 iiuliviiljial (ul(ipt(dii)ns. From these we nnist distinguish 

 chnrcirtcriKtic (ulapliitinns, or ad\':intageous peculiarities lie- 

 longing to whole groups. Of such adajitafions the charac- 

 teristics of clematis above referreil to may servo as examples; 



