156 INDIVIDUALITY IN ORGANISMS 



lower down more readily than these with their lower 

 rate are able to reverse the whole established proto- 

 plasmic gradient higher up. If. however, a new gradient 

 at a lower level becomes established while the dominant 

 region above is inhibited, it is conceivable that it may in 

 time, by its gradual extension in the stem, obliterate 

 more or less completely, or perhaps reverse, the original 

 gradient and so dominate regions higher up, at least to 

 some extent. This is apparently the case in the seedling 

 mentioned above (p. 153) when the axillary shoots are 

 allowed to grow long enough while the main growing 

 shoot is inhibited. Under such conditions they are 

 apparently able to inhibit what was originally the domi- 

 nant region of the whole plant. 



It is often possible to isolate a part of the plant from 

 the dominance of the growing tip merely by cutting the 

 vascular bundles connecting the two parts. The devel- 

 opment of buds on the leaves of certain plants may be 

 induced by severing the chief vein or veins of the leaf, 

 other tissues remaining intact. In such cases buds 

 appear peripheral to the cut, usually near the veins, 

 but in some plants on the leaf margins. 



The inhibiting influence is not confined to the grow- 

 ing tips of stems, for it has been shown that a leaf plays 

 apart in inhibiting the growth of the bud in its axil. 

 Removal of the leaf or inhibition of its activity may 

 bring about outgrowth of the bud, if the inhibition 

 from other souces is not too complete. In certain cases 

 it has been shown that one part of a leaf may inhibit 

 other parts. In Cyclamen persicum, for example, the 

 young seedling (Fig. 86) possesses at first only a single 

 leaf, one of the cotyledons. Removal or inhibition 



