THE INHIBITORY EFFECT OF AN APICAL LEAF 125 



shoot opposite the leaf was cut out in all four stems. In all these 

 stems the apical leaf was rather large. The stems bent geotropic- 

 ally so that during the experiment, which lasted from Mar. 16 to 

 Apr. 3, 1923, they assumed the shape of a U, the concavity being 

 on the upper side. 



The stems in which the apical leaf was on the lower side (Fig. 

 101) formed a shoot in the second node basally from the leaf and 

 on the upper side of the stem. This was to be expected since 

 the upper side of the stem is opposite to that of the leaf. This is 

 what happens also when the stem is suspended vertically. But 

 some of the stems formed shoots also or exclusivelv in the first 



4/*' 



Fig. 101. — Stems originally horizontal with leaf on lower side. Shoot formed 

 in second node on upper side or in both first and second node on upper side. 

 Mar. 16 to Apr. 3, 1923. 



node basally from the leaf, and this is different from what would 

 have happened if the stem had been suspended vertically, since 

 in the latter case no shoots would have been formed in the first 

 node, provided the leaf was not too small and the stems 

 sufficiently young. 



When the apical leaf is on the upper side of the stem suspended 

 horizontally (Fig. 100), the results are still more striking. In 

 this case the stem sometimes forms no shoot at all, or if it forms 

 a shoot its appearance is delayed for some time. The shoot is 

 formed in the second node basally from the leaf on the lower 

 side of the stem (which is opposite to that where the leaf is 

 attached). 



It is not difficult to understand these results on the basis of 

 the assumption that there are two channels for the flow of sap in 

 the stem, one through preformed vessels and one through the 



