THE INFLUENCE OF THE LEAF 



71 



was delayed and limited in comparison with that of a stem pos- 

 sessing a leaf. The leaf furnished, therefore, something more 

 than water for the formation of the roots. The same reasoning 

 holds for the influence of the leaf on the formation of shoots in the 

 stem, since the stem dipping into water could absorb all the water 

 needed for shoot formation. 



The total results of the experiment are given in Table XVL 



Table XVI 



Dry 



weight of 

 leaves, 

 grams 



Dry 



weight of 



stems, 



grams 



Dry weight of 

 regenerated 



Shoots, 

 grams 



Roots, 

 grams 



I. Six half stems with leaves. . . . 



II. Six half stems without leaves. 



III. Six leaves 



0.136 



0.102 



Figure 52 shows incidentally that in this case the leaf left in 

 connection with the half stem did not produce any shoots or roots. 

 This is a confirmation of the statement made in an earlier chapter 

 that if the piece of stem to which a leaf is attached is sufficiently 

 large and if the leaf is in air the formation of shoots and roots in 

 the leaf is generally completely suppressed. This will be sup- 

 ported by a large number of the experiments which will be 

 described in the remaining chapters of the book, wherever the 

 piece of stem connected with the leaf is large and the leaf is in air. 



In this experiment the regeneration of roots was completely due 

 to the material sent out by the leaf into the stem and over two- 

 thirds of the dry weight of the shoots regenerated by the stem 

 was furnished by the sap from the leaf. Yet the character of the 

 regeneration in the stem was as clearly polar as in the completely 

 defoliated stems described in a preceding chapter. 



It was to be expected that the quantity of regeneration in an iso- 

 lated piece of stem should vary with the mass of the leaf attached. 

 In 8 stems, of 5 nodes each, all the leaves except those in the third 

 node were removed and the stems were split lengthwise. One 

 leaf remained intact, while the sister leaf was reduced by cutting 

 away about two-thirds. The stems were suspended so that 

 their base dipped into water. Figure 53 shows that the half 

 stems with reduced leaves produce a correspondingly smaller 

 mass of apical shoots and roots. Table XVII gives the results. 



