THE INHIBITORY EFFECT OF AN APICAL LEAF 131 



of a temporary retardation of shoot formation (inhibition of the 

 second order). When the apical leaf is reduced in size the 

 growth of the stem inside the path of the descending current will 

 be less and hence the inhibitory effect on shoot formation (both 

 of the first and second order) will also be less. This assumption 

 explains the phenomena of inhibition qualitatively as well as the 

 hormone hypothesis and has the advantage of being in harmony 

 with the theory of polarity. But how the growth in the stem 

 inhibits the growth of shoots remains unexplained. 



