THE CHEMICAL MECHAMSM OF IIEGENERATION 13 



It miglit be argued tliatour experimcnts would be more satis- 

 factory if Ihe increase in the amount of dry weight of the stem 

 were exactly equal to its inhibiting efïect upon the shoot pro- 

 duction in the leaf instead of being in excess. Yet, the resuit 

 we actually obtained is oxactly the one which in the nature of 

 the circumstances should be expected, since the leaf « natu- 

 rally » sends its malerial into the stem and as a conséquence 

 the stem cari draw from the leaf material more rapidly than 

 can be done by notches of the leaf. AVhen the notches begin to 

 grow ont new channels for the tlow of sap to them will gra- 

 dually bave to be developed, while such conducting vessels or 

 channels from leaf to stem are a part of tlie normal leaf. 

 Thèse ideas are supported byanumber of observations. Thus 

 it can be sliown that the shoots which form in the free bud of 

 a stem, as in Fig. 1, develop more quickly Ihan the shoots in 

 the notches of a leaf, even if the apex of the latter dips into 

 water, thus indicating that the material of the leaf coUects more 

 rapidly in the stem than in the notches. Moreover, a pièce of 

 stem of a certain size will inhibit the shoot production in the 

 notches of a leaf completely Avhen the leaf is small, while the 

 inhibition will be less complète when the leaf is larger. If the 

 chances for the flow of material to the notches were the same 

 as for the flow to the stem we should expect to find a constant 

 coefficient of distribution of material betvveen notches and 

 stem which is not the case. 



Finally, the stem not only inhibits shoot production in the 

 leaf but also root production. Il" this is due to the absorption 

 of material by the stem the latter should gain more than the 

 équivalent of the inhibiting effect on shoot production alone. 



III. 



The proof that the dry weight of a pièce of stem left in con- 

 nection with a leaf increases more than necessary to account 

 for the inhibitory effect of the stem upon shoot production in 

 the leaf, becomes of great significance when we investigate 

 what becomes of this material in the stem. We notice that it 

 is utilized for at least three ditferent forms of growth in the 

 stem, namely, first, the formation of shoots from the dormant 



