6 ANNALES DE L'INSTITUT PASTEUR 



gives llie rcsiills. The loaves dippcd willi Ihcir apices inlo 

 water. 



Table IV. 



ïhese experiments show that if we rediice the mass ol'one set 

 of leaves by ciitting- out pièces in the cenler, while their sister 

 leaves remain intact, both sets will producc in eqiial time and 

 under equal conditions shoots in proportion to their masses. 

 This law explains the inhibition of shoot production in a leaf. 

 Observation shows that, when we isolate a leaf of Bryophijllmn 

 calijcinum^ those notches will as a rule grow out first into 

 shoots where the leaf is thickest ; as soon as thèse grow out 

 the rest of the notches is prevented from growing, inasmuch 

 as ail the material available in the leaf now flows into the 

 notches where shoots first begin to grow out. ïhis with- 

 drawal of the material from the other notches détermines the 

 inhibition of growth in thèse notches, since the material avail- 

 able at any time for shoot production is, as we bave seen, 

 limited and fixed by the mass of the leaf. When we eut a leaf 

 into as many pièces as there are notches, they may ail rege- 

 nerate since no other notch can withdrawthe material available 

 for the growth of each. 



We bave it entirely in our power to décide which notch in 

 a newly isolated but intact leaf shall grow out first; ail we 

 iieed to do is to dip that notch into water. We do not know 

 defmitely how the increase in water supply can accelerate the 

 growth of a notch, though we may guess that an accélération 



