

1917] 



LOEB—BR ] OPH YLL UM 



27 



I. Influence of the presence and absence of leaves 



Fig. 1 illustrates the influence of the presence and absence of 



curvature 



The 



stems to the right had no leaves and bent very 



other leaves were removed) and bent much more 



(while 



The 



photograph was taken on the eleventh day after the experiment was 



begu 



It is noticeable also that the stems containing leaves 



Fig. 2 



formed roots (in their basal nodes) much more rapidly than the 

 stems deprived of all leaves. This experiment, representing the 

 accelerating influence of the apical leaves upon both root formation 

 and geo tropic curvature, never fails; and the same may be said of 

 most of the experiments described in the following pages. 



11. Influence of the position of the leaf on the stem upon 



geotropic curvature and organ formation 



In the following experiment only one leaf was left on the stem. 

 It was found that it made a great difference whether this leaf was 

 at the apex or at the base. This is illustrated by fig. 2. On the 







