THEORY OF THE GBOWTH OF CUTTINGS. 417 



Before finally giving the conclusions for which these facts give 

 part of the data, it will be well to state clearly what is meant by 

 the after-effect of gravitation, which is not a well-defined term. 

 Thus, for instance, Vochting * believes that his innate growth- 

 force has arisen as a " gradually accumulated function " of gravi- 

 tation and light. Such an effect might, no doubt, be called an 

 after-effect ; but it is not in this sense that I use the word : I take 

 it to mean the growth-tendencies which are produced in an organ 

 through the action of gravitation during the development of the 

 constituent cells of the organ in question. It is in this sense that 

 Sachs f alludes to the effect produced by the previous action of 

 gravitation ; for he speaks of an organ kept in slow rotation during 

 its growth as being thus freed from the predisposing influence of 

 gravitation. 



Since, then, we have seen that Brambles, whether they have 

 grown above or below the horizon, tend to produce both leaf- 

 bearing and root-bearing branches near the apex, we cannot 

 account for the fact through the after-effect of gravitation, but 

 must believe in some internal morphological force. 



Thus the result of the experiments confirms the conclusions 

 arrived at with regard to the normal growth of roots at the end 

 of branches (see p. 412). 



Vochting has made the interesting observation (Bot. Zeitung, 

 1880, p. 595) that cuttings made from branches of weeping varieties 

 of various trees behave like cuttings of ordinary trees, and produce 

 roots at their base and branches at their apex. This fact shows 

 that the distribution of root-growth and branch-growth is exactly 

 the reverse of that in ordinary cuttings, when considered in relation 

 to gravitation ; but it does not, I think, prove the existence of a 

 morphological force. It might be assumed, by a modification of 

 Sachs's hypothesis, that the sensitiveness to gravitation has been 

 reversed in the branches of weeping trees, and that the tendency 

 to produce shoots at the apex is a consequence of this kind of 

 sensitiveness. The cutting of a weeping tree would thus differ 

 from an ordinary cutting just as an apogeotropic organ differs 

 from a geotropic organ, in having a reversed sensitiveness to 

 gravitation. But such an objection cannot be urged against the 



which had grown apex downwards in a dependent position, with the result 

 that the most apical buds grew into side-shoots, which assumed in some cases a 

 root-bearing character. 



* Bot. Zeitung, 1880, p. 596 : " Eine allmahlich accumulate Function der 

 geuaiinten beiden Krafte." t Loc. cit. p. 475. 



