380 



INFLUENCE OF GRAVITY ON ARRANGEMENT OF ORGANS 



II. 



The idea that a collection of sap occurs in the lower parts of a leaf 

 suspended in a vertical plane can be demonstrated through the fact 

 that leaves thus suspended in moist air form a reddish or purple 

 pigment which has a tendency to collect in the lower parts of such a 

 leaf. Fig. 4 shows two leaves with this pigment. The leaves had 

 been suspended in moist air from April 17 to May 14, 1919. The 



Fig. 4. Leaves suspended in moist air. Collection of reddish or purplish pig- 

 ment in lower halves of the leaves, following the vessels. It is also obvious that 

 the pigment collects more densely near each notch where a shoot or roots grow out. 

 The leaves of the new shoots formed are full of pigment while the roots are free 

 from it. Duration of experiment, Apr. 17 to May 14, 1919. 



reddish or purple pigment is indicated in the drawing by black 

 stippling. It is obvious that the pigment collects in the lowest parts 

 of the leaf, that it follows the vessels, and that it also flows into the 

 young leaves, thus supporting the view that a deflection of the sap 

 flow towards the new shoots occurs in such a leaf. It does not, 



