256 



BOTANICAL GAZETTE 



[OCTOBER 



effective, if sufficient in degree, in inducing more or less outgrowth 

 of leaf buds, provided the leaf concerned was in saturated air or 

 water. Slight superficial injury, even though it extended com- 

 pletely around the petiole, had little or no effect. An injury to 

 the petiole of one leaf sufficient to induce outgrowth of some of the 

 buds of that leaf usually induced outgrowth of some buds on the 

 opposite leaf, and sometimes also on leaves of the next node above 

 or below, if these were in moist air or water. Such mechanical 

 injury by partial section of the petiole or by compression, how- 

 ever, was less effective than low temperature, unless the injury 

 was sufficient to interrupt physiological continuity to a very con- 

 siderable degree. Cuts half way through the petiole, for example, 

 brought about development of some buds on the leaf, but usually 

 of only a few, and in the case of lateral cuts the buds growing were 

 not necessarily on the same side as the cut. Mechanical compres- 

 sion of the petiole by a screw clamp gave similar results. Fig. 1 



shows a case in which 

 the petiole of the leaf A 

 was compressed to half 

 its thickness by the 



screw clamp. The leaf 

 A, the opposite leaf B, 

 and one leaf C of the 

 next pair below were par- 

 tially submerged. On 

 leaf A five buds grew 

 out of eighteen sub- 

 merged; on leaf B, seven 

 out of seventeen sub- 



■^ 



Fig. 1 



me 



advanced than those of A. 



grow 



out of seventeen buds submerged, but this growth consists merely 



visible 



similar 



experiment slightly less compression resulted in outgrowth of 

 only three buds out of twelve submerged on the leaf with com- 

 pressed petiole, and no growth in B and C. Comparison of these 

 results with those obtained by low temperature described later 



