418 MR. F. DARWTN ON THE 



conclusions with regard to the growth of Brambles ; for a Bramble, 

 which may be said to produce weeping and erect branches on a 

 single plant, could not, by any kind of sensitiveness to gravita- 

 tion, always produce its roots at the apex of the branches. 



The second object which I had in view in working at the Bramble 

 was to answer the questions, Why is it that a plant is divisible 

 into cuttings having certain growth-tendencies ? How can it help 

 the plant in its normal growth, to possess the properties which 

 exist in the artificially produced life-unit ? I have been able to 

 form a hypothesis with regard to the Bramble which may prove to 

 be applicable to other plants. When any injury happens to the 

 apical end of a bramble -branch (the basal end being in continuity 

 with the parent plant), one or more buds grow out into side- 

 branches. These side-branches may either be ordinary leaf- 

 bearing or else root-bearing branches. In either case they perforin 

 the function which the injured part of the parent branch would 

 have performed. And this power of carrying on the function of 

 a part, in spite of an injury received, must clearly be advantageous 

 to the plant *. The question then arises, Which bud is in the 

 best position to carry on the disturbed function ? And it seems 

 quite clear that the buds morphologically nearest to the apex must 

 be in the best position for carrying on the function of the apex. 

 If, for instance, a branch growing down towards the earth is in- 

 jured, and thus prevented from bearing roots at its natural apex, 

 the most apical bud will be in the best position for producing a 

 rooting branch at least cost of growth. Again, the distribution 

 of the Bramble is facilitated by the power which the branches have 

 of creeping along the ground, and taking root many feet (e. g. , 

 8 feet) distant from the parent plant. If such a branch is 

 injured, the most apical bud will be in the best position for con- 

 tinuing the duty of providing for the distribution of the plant, 

 and thus carrying out this function of the injured apex. 



* Vochting says (• Organbildung,' p. 107) that " If the actually or poten- 

 tially unlimited growth of the stem or root is interrupted by section, it (the 

 growth) is continued at the ends thus formed, either by rudiments (Anlagen) 

 already present there or by new formations. The roots at the apical end of 

 a root, and at the apical end of a branch, represent the continuation of the 

 interrupted apical growth of the root; the buds at the apical end of a branch, 

 or at the basal end of a root-cutting, represent the continuation of the inter- 

 rupted apical growth of the branch." (The phrase which I have translated 

 *' represent the continuation " &c. is " stellen die Folge der Unterbrechuog aei 

 Spitzenwachsthums . . . dar.") 



