86 THE SURVIVAL OF THE UNLIKE. [ill. 



branches and flowers and seeds when it is borne upon 

 its parent plant. And I should remind you that those 

 plants which are not readily multiplied by cuttings are 

 generally propagated by grafting, which, for illustration, 

 amounts to the same thing, for we only substitute the 

 stock of another plant for the soil. Plants of the most 

 various kinds are readily multiplied by graftage. Even 

 tuberous herbaceous stems, which are not commonly 

 associated with the art of the grafter, unite with ease. 

 One of the latest investigators in this field is a French- 

 man, Daniel, and his conclusions upon the physiology 

 of grafted plants show that the physiological modi- 

 fications in these plants are largely such as arise from 

 physical causes, showing that the parts still preserve 

 their essential autonomy. 



Now, if every plant varies in the number of parts, or 

 phytons, of which it is composed, it follows that this 

 number must be determined by agencies which act im- 

 mediately upon the given plant itself. We all know that 

 the number of these parts is determined very largely by 

 environment. A dozen plants springing from the same 

 capsule may vary immensely in the numbers of their 

 branches, leaves and flowers, and this variation is gen- 

 erally obviously correlated with amount of food, amount 

 of space which the plant is allowed to occupy, and other 

 physical conditions which affect its welfare. But we 

 not only find that no two plants have the same number 

 of parts, but that no two branches in the same plant are 

 alike. One part grows longer, one more erect, one has 

 greener leaves, one bears more fruit. So, too, there 

 may be different forms of flowers on the same plant, a 

 subject to which Darwin has devoted an entire volume. 

 We know, also, that this variation amongst the sister- 



