INHIBITORY EFFECTS OF A SECOND ORDER 



115 



about one-half of the quantity of shoots that 1 gram of dry weight 

 of leaf formed through the ascending sap. 



Now in these experiments no shoots or roots were formed in 

 the leaves themselves. On the basis of the experiments mentioned 

 in Chapter VI, we must conclude that the leaves sent out the 

 greater part of their material into the stem in both experiments 

 and that hence the diminution in the quantity of shoot production 

 by the descending sap must be attributed to the fact that not 

 quite as much of the material sent out by the apical leaf was 



Fig. 90. — Shoot formation in stem with basal leaf. 



utilized for shoot formation as was utilized in the case of the basal 

 leaf. The stem must have retained in some form a greater part 

 of the material sent out by the apical leaf. That such a reten- 

 tion of material in the stem seems actually to occur to a greater 

 extent in the case of the descending than in the case of the 

 ascending sap is also shown by the fact that the shoot formation 

 in a piece of stem with an apical leaf is delayed and diminished 

 the more, the greater the distance between the place of shoot 

 formation and apical leaf; while no such relation exists in the 

 case of the ascending sap. 



Six young stems with one apical leaf each were suspended with 

 their base in water. In this case each of the stems formed one 

 shoot opposite the leaf (Fig. 91). The dry weight of the 6 leaves 



