JACQUES LOEB 



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each of the two buds in the first node. Fig. 7 shows the control 

 experiment; namely, six stems each with one whole leaf at the apex. 

 Not a single stem has formed a shoot in the first or any other node 

 below the leaf. Both sets of experiments were carried out simul- 

 taneously and both sets of plants were side by side in the same 

 flower bed. 



When we reduce the mass of a leaf 10 days after the experiment is 

 started and when the new shoots begin to form, the inhibitory effect 

 nevertheless becomes noticeable. 



Fig. 8. Proof that traces of inhibition of a leaf upon shoot formation are also 

 noticeable in the more apical shoots. Old leaf left at first node below the apical 

 node. The two Leaves 1 and 2 of the new shoot in the apical node which are 

 normally of equal size show a constant difference, Leaf 1 (on the side where the 

 old leaf is) being smaller than Leaf 2 (on the opposite side). 



Demonstration of the Inhibitory Influence of a Leaf on Shoot Formation 

 in a More Apical Node. 



We can state as a general rule that a leaf accelerates the growth 

 of shoots at the apex and prevents or retards it in the basal parts of 

 the stem. The leaf has, however, also a slight inhibitory effect on 

 the more apical buds. In order to prove this it is necessary to make 

 experiments like those represented in Fig. 8. In a number of topped 



