14 



REGENERATION 



The experiment shows that the mass (in dry weight) of shoots 

 and roots regenerated by isolated sister leaves of Bryoyhyllmn 

 varies under equal conditions approximately with the mass 

 (in dry weight) of the leaves. On the assumption that the mass 

 of material produced in sister leaves under the influence of 

 light varies with the mass of the leaves, it is suggested that the 

 quantity of regeneration is determined by the mass of material 

 produced in the leaf under the influence of hght. 



That the shoot production in the small apical pieces (la) is 

 comparatively a little greater than in the large pieces is probably 



Fig. 16. — Root and shoot formation in whole leaf and in sister leaf (from which 

 the left half is cut off) dipping with their apices in water. Diagrammatic. 



due to the fact that the sap has not so far to travel to reach the 

 notches where growth occurs in the small pieces (la) as in the 

 larger pieces of leaf (2 and Ih), and that comparatively more of 

 the material available in a piece of leaf can go into the new roots 

 and shoots when the piece is small than when it is large. 



Experiment 3. — One set of 6 isolated leaves (Set II) remained 

 intact while the mass of each leaf of the other set was reduced to 

 approximately one-half by cutting away one side of each leaf 

 (Set I, Fig. 16). The masses of the two sets of leaves were there- 

 fore no longer equal but had approximately the ratio of about 

 1:2. It was to be expected that the dry weights of the shoots 

 and roots produced by the two sets of leaves should also be in the 

 ratio of about 1 : 2, and this was the case (within the Hmits of 

 the possible accuracy of such experiments) (Table III). One 

 gram dry weight of leaves produced within the limits of the 



