THE INFLUENCE OF GRAVITY 



89 



Table XX.^ — Showing That the Mass of Air Roots in a Stem Diminishes 

 WITH THE Mass of the Apical Leaf. The Stems Were Split Longi- 

 tudinally, Each Half Possessing One Sister Leaf at the Apex. 

 In One Set the Leaf Was Left Intact, in the Other it Was 

 Reduced in Size by Cutting Off Part of the Leaf. 

 The Stems with Reduced Leaf Invariably Formed 

 a Small Mass of Roots 



When the stems are prevented from geotropic bending as in 

 Fig. 66 roots are nevertheless formed in abundance on the 

 lower side of the stem. And, furthermore, if the stem is bent 

 passively (by tying it to a piece of wood) so that its convex side 

 is directed upwards as in Fig. 67 the roots form nevertheless on 

 the lower side. This all is in harmony with the assumption 

 that the excess of root formation on the lower side of a stem 

 suspended horizontally in moist air is due to a collection of tissue 

 sap on the lower side of the cortex of the stem. 



