432 



BOTANICAL GAZETTE 



[DECEMBER 



The rigidity curve shows at first only a slight upward slope, but 

 when the internode is approaching its full length there is a sudden 

 and extensive upward turn in the curve. The coefficient of rigidity 



Fig. 5 



curve shows the same general properties, but careful study shows 

 that its first slope, that is, up to the point e, compared with the 

 initial value of this coefficient, is much less than the ratio between 



