no REGENERATION 



dipping into water. When kept in air, small pieces of stem 

 without leaf form Kttle or no callus. When a piece of stem 

 with one pair of sister leaves is split longitudinally and one leaf 

 is reduced in size (Fig. 85) the stem connected with the smaller 

 piece of leaf produces in the same time and under the same 

 conditions less callus at the base than the piece of stem connected 



Fig. 85. — Stem connected with whole leaf forms more callus than stem connected 

 with sister leaf reduced in size. Nov. 15 to Dec. 12. 



with the larger piece of leaf. The experiment lasted from 

 Nov. 15 to Dec. 12. 



The callus formation at the base of a piece of stem increases 

 therefore with the mass of the apical leaf, as does also the inhibit- 

 ing influence of an apical leaf on shoot formation in its path. 



When the apical leaf is near the base the callus formation 

 occurs more rapidly and is larger than when the apical leaf is 

 further from the base; since in the latter case the descending sap 

 from the leaf has a greater distance to travel before it reaches the 

 base and part of its material should be consumed by the stem 

 before it reaches the base. This is demonstrated by Fig. 86 



