306 DARWINISM ' chap. 



by floating in rivers and lakes, and thus reaching other locali- 

 ties. During the elevation of land areas this method would 

 be very effective, as the new land would always be at a loAver 

 level than that already covered Avith vegetation, and therefore 

 in the best position for being stocked A^th plants from it. 



The other modes of dispersal of seeds are so clearly adapted 

 to their special wants, that Ave feel sm-e they must have been 

 acquired by the jDrocess of variation and natural selection. 

 The hooked and sticky seeds are ahvays those of such her- 

 baceous plants as are likely, from their size, to come in 

 contact Avith the avooI of sheep or the hair of cattle ; Avhile 

 seeds of this kind never occur on forest trees, on ac^uatic 

 plants, or eA^en on very dAvarf creepers or trailers. The 

 winged seed-vessels or seeds, on the other hand, mostly belong 

 to trees and to tall shrubs or climbers. We have, therefore, a 

 very exact adaptation to conditions in these different modes of 

 dispersal ; AA'hile, Avhen Ave come to consider individual cases, 

 we find innumerable other adaptations, some of Avhich the 

 reader Avill find described in the little Avork by Sir John 

 Lubbock already referred to. 



Edible or Attractive Fruits. 



It is, hoAvever, AA^hen Ave come to true fruits (in a popular 

 sense) that Ave find varied colours CAddently intended to 

 attract animals, in order that the fruits may Ije eaten, Avhile 

 the seeds pass through the body undigested and are then in 

 the fittest state for germination. This end has been gained in 

 a great variety of ways, and Avdth so many corresjjonding 

 adaptations as to leave no doubt as to the value of the result. 

 Fruits are pulj^y or juicy, and usually sweet, and form the 

 favourite food of innumerable bii'ds and some mammals. They 

 are ahvays coloured so as to contrast Avith the foliage or 

 surroundings, red being the most common as it is certainly the 

 most conspicuous colour, bi;t yelloA\^, i)urple, Ijlack, or Avhite 

 being not uncommon. The edible portion of fruits is developed 

 from different parts of the floral envelopes, or of the ovary, in 

 the various orders and genera. Sometimes the calyx becomes 

 enlarged and fleshy, as in the apple and pear tribe ; more 

 often the integuments of the ovary itself are enlarged, as in 

 the plum, peach, grape, etc. ; the receptacle is enlarged and 



