30 



REGENERATION 



In the leaf without stem the red pigment collected in the lower 

 part where three shoots were formed, while in the leaf attached 

 to a stem it collected near the petiole of the leaf. 



In order to prove quantitatively that the inhibitory action of a 

 piece of stem on root and shoot formation in a leaf is due to the 



Fig. 27. — Sister leaves dipping with their apices in water. Leaf a, without 

 stem, has formed 4 shoots in 4 different notches. Leaf ai, attached to a piece 

 of stem, has just commenced to form 1 tiny shoot in 1 notch. The material 

 which caused shoot production in leaf a was utilized by the stem in leaf ai for 

 the production of a large shoot on the stem, for callus formation at the basal 

 end of the stem, and for a slight geotropic curvature. The drawing was made 

 7 weeks after the beginning of the experiment. 



flow of material from the leaf into the stem the following method 

 was used: 



Small pieces of a stem of Bryophyllum., containing 1 node with 

 2 leaves each, were cut out from a plant. Each piece of stem was 

 spht longitudinally through the middle (Fig. 29), to make the 



