THE ROLE OF THE INHIBITING EFFECT 



61 



seems to be as follows. There is, as a rule, enough sap present in 

 a piece of stem at the beginning to permit the starting of root 

 formation in many nodes, and of shoot formation in more nodes 

 than the most apical ones. More sap, however, will collect 

 at the two ends of the stem than in the middle and this causes a 

 slight acceleration of root formation at the base and of shoot 

 formation at the extreme apical node. This causes as a sec- 

 ondary result a vigorous flow of the sap from the whole stem 



Fig. 47. — Proof that the polar character of regeneration in a stem suspended 

 vertically is independent of gravity. Stem in Fig. 47 inverted, with apex dip- 

 ping into water and base above. Shoots commence to appear at the three most 

 apical nodes, and roots in the intermediate nodes between the most apical and 

 basal one. Mar. 4 to 12, 1919. 



to these two ends whereby the growth in the intermediate nodes 

 is inhibited. The organs which commenced to grow in the 

 intermediate nodes now stop growing or wilt. 



The question presented itself to what extent this result is 

 determined by gravity. In Figs. 43 to 45 the stems were in a 

 vertical upright position. It was found that the result was the 

 same when stems were suspended in moist air in an inverted 

 position, the apex being below and the base above. Figures 47 



