THE INHIBITORY EFFECT OF AN APICAL LEAF 129 



observed in the stems drawn in Figs. 102 to 104, but was a general 

 result. It is incompatible with the idea that the initial inhibitory 

 effect of the apical leaf on the shoot formation in stem a was due 

 to an inhibitory hormone, since it is contradicted by the viltimate 

 result that the shoot in stem a exceeds in mass those of stems h 

 and c. 



Similar phenomena of inhibition (of the second order) are 

 observed when the leaf is below. Young stems (as in Fig. 

 105, a and h) were suspended horizontally, the leaves dipping 

 into water, b had a large leaf, the leaf in a was considerably 



Fig. 105. — Leaf on lower side of stem. Stem b, with whole leaf, has not yet 

 commenced to form a shoot, while the stem with a smaller piece of leaf has com- 

 menced to form shoots. May 16 to 24, 1923. 



reduced: The shoot formation commenced a little earlier in a 

 than in h. The drawing was made on the eighth day. Five 

 days later, that is on the thirteenth day of the experiment, the 

 shoot in the stem with a large leaf exceeded in mass the shoots in 

 the stem with a small leaf (Fig. 106). On the twenty-third day 

 the experiment was interrupted and the dry weight of the leaves, 

 shoots, and stems was determined. Two sets each with 5 stems 

 were used for the experiment. The dry weight of the 5 whole 

 leaves (6 and 6i in Figs. 105 and 106) was 1.258 grams and their 

 stems produced in all 370 milligrams of shoots; or 1 gram of leaves 

 produced 293 milligrams of shoots. The total dry weight of the 

 5 reduced leaves (a and ai in Figs. 105 and 106) was 0.328 gram 

 and the stems produced only 111 milligrams of shoots; or 1 gram 

 dry weight of leaf produced 337 milligrams dry weight of shoots, 



