90 REGENERATION OF BRYOPHYLLUM CALYCINUM 



material furnished by the leaf. This is not surprising since we know- 

 that the leaf is the organ where the material for new growth in the 

 plant is manufactured. It is also to be expected that in pieces of 

 stems of different mass but without leaves the mass of shoots regen- 

 erated will increase with the mass of the piece of stem. The writer 

 has already published experiments indicating that this is true,* though 

 he has not yet made quantitative determinations to find out whether 

 the law of proportionality holds in this case also. 



IV. 



The law of proportionality between mass of the leaf attached to the 

 base of a stem and mass of shoot produced apically from the leaf can 

 be proved for other cases also. If we cut out a piece of stem with 

 only one node containing two leaves such a piece possesses only two 

 buds capable of developing into shoots; namely, one in each of the axils 

 of the two leaves (Fig. 5). These axillary buds grow out more rarely 

 and more slowly than the free buds at the apex of a piece of stem. 

 Fourteen pieces of stem with one node and two leaves each were cut 

 out from plants and each piece of stem was spht longitudinally between 

 the two leaves. One leaf remained always intact, the other leaf was 

 reduced by cutting off part of the leaf (Fig. 5). Eight of these fourteen 

 pieces of specimens formed axillary shoots. It seemed of interest to 

 find out whether the mass of these shoots was approximately in pro- 

 portion to the mass of the leaves. This was the case (Fig. 5), The 

 duration of the experiment was 45 days. The apices of the leaves 

 dipped into water. 



a. Weight of 8 whole leaves, 10.968 gm. Weight of 8 shoots produced in their 

 axil, 1 .8025 gm. Mg. of shoots produced per gm. of leaf, 164. 



b. Weight of 8 reduced sister leaves, 3.586 gm. Weight of 8 shoots produced 

 in axil, 0.5895 gm. Mg. of shoots produced per gm. of leaf, 164. 



The mass of axillary shoots produced by each set of sister leaves was, 

 therefore, in direct proportion to the mass of the leaves. 



"Loeb, Bot. Gaz., 1915, Ix, 249. 



