438 



SCIENCE 



[N. S. Vol. XLV. No. 1166 



TABLE in 



Leaves Kept in Moist Air 



holds. In spite of this and some other sources 

 of error the results are in fair agreement with 

 the theory. 



TABLE IV 



These observations agree with the assump- 

 tion that the growth of dormant huds is deter- 

 mined hy and is in proportion to the quantity 

 of a certain material available for the huds. 



4. In the previous publications attention 

 h&d been called to the fact that in an isolated 

 leaf only a few of the numerous notches grow 

 into shoots and this had been explained on 

 the assumption that those notches which hap- 

 pen to grow out first attract all the material 

 from the leaf and thereby prevent the other 

 notches from growing. This suggestion was 

 supported by the observation that if a leaf is 

 cut into isolated pieces each possessing one 

 notch, each notch gives rise to a new shoot 

 (provided that the piece is not too small). 

 The shoots in the subdivided leaf grow more 

 slowly than the less numerous shoots of whole 

 leaves. On the basis of our quantitative 

 method we should therefore expect that if of 

 two isolated sister leaves one (a) is left intact 

 while the other (h) is cut into as many pieces 

 as it contains notches, the ratio of the weight 

 of shoots produced to the weight of the leaf 

 should be equal in both leaves; in spite of the 

 enormous difference in the number of shoots 

 produced. If a leaf is divided into two halves 

 a and h, and half i further subdivided into 

 as many pieces as there are notches, the numer- 

 ous shoots produced by the isolated notches 

 should not weigh more than the few produced 

 in the intact half. 



These experiments encounter the difficulty 

 that if the piece of a leaf is below a certain 

 size its notch will fail to produce a shoot; and 

 if the piece approaches this lower limit its 

 shoot production is still considerably retarded 

 so that the law of proportionality no longer 



The experiments support the view that whep. 

 in a leaf shoots are formed they withdraw 

 material from the other notches and that it is 

 this withdrawal of material which prevents 

 the other notches from growing. 



5. By the same reasoning we should expect 

 that the inhibition in the growth of the notches 

 of the leaf by a piece of stem (referred to in 

 the beginning of this note) is due to the ab- 

 sorption of material from the leaf by the stem. 

 In corroboration of this assumption the writer 

 has been able to show that the inhibiting effect 

 of the stem upon leaves of the same size in- 

 creases with the mass of the stem. It has also 

 been possible to show by quantitative experi- 

 ments that the inhibiting effect of pieces of 

 stem of the same size upon leaves of different 

 size diminishes when the size of the leaves 

 increases. We may say tliat the stem acts upon 

 the leaf as if it reduced the size of the latter. 



But the withdrawal of material by another 

 organ is not the only way by which the growth 

 of a bud is inhibited. The main condition for 

 growth is that the material reaching the bud 



