GROWTH OF ROOTS AND SHOOTS IN THE LEAF 



35 



and shoots formed in each set of leaves was measured in each set 

 of experiments. 



Table XI. — Dry Weight of Roots and Shoots Formed in Detached 



Leaves and in Leaves Connected with Half Stems in the 



Same Experiment as in Table X 



Experi- 

 ment 

 No. 



Duration 



of 



experiment, 



days 



1. Detached 

 leaves 



Dry weight 



Roots, 

 grams 



Shoots, 

 grams 



Total, 

 grams 



2. Leaves with 

 half stems 



Dry weight 



Roots, 

 grams 



Shoots, 

 grams 



Difference in 

 Total, dry weight of 

 grams 1 and 2, 



grams 



30 

 33 

 33 

 30 

 30 



0.475 

 0.321 

 0.477 

 0.369 

 0.312 



Total.. .1.954 



The dry weight of the material which was given off by the leaves 

 to the pieces of stem attached to them was 2.393 grams, while 

 1.954 grams was the excess of the dry weight of roots and shoots 

 formed in the leaves entirely detached from stems over the dry 

 weight of roots and shoots formed in the leaves with stems 

 attached. This proves that the inhibitory effect of the stem on 

 root and shoot production in the leaf is due to the fact that the 

 material available for regeneration in the leaf flows into the stem. 

 The amount of material given by the leaves to the stem is roughly 

 20 per cent greater than the amount which is utilized in the excess 

 production of roots and shoots in the detached sister leaves. 

 This excess is accounted for by the fact, discussed in the preceding 

 chapter, that not all the new material produced by assimilation in 

 the detached leaf goes into the formation of roots and shoots 

 in the leaf, but that about 33 per cent of this material is used for 

 the growth of the leaves themselves. When a piece of stem is 

 attached to a leaf, part of this reserve material may also go into 

 the stem. 



When the axillary bud of the half piece of stem grows out, 

 which does not usually happen, the flow of material from the leaf 

 into the stem is much more considerable; and, accordingly, as is 

 shown in the following experiment the inhibitory influence of 

 the stem on regeneration in the leaf is still more considerable. 



