10 



In adu.lt leaves of C. succirubra alcaloid can be demonstra- 

 ted to be présent (at certain times) in ail mesophyll cells 

 but always in less quantity than in the younger leaves. 

 Frequently, though not always, it can be demonstrated that 

 the mesophyll cells near the vascular bundles contain mo- 

 re alcaloid than the other mesophyll cells; one sees this occa- 

 sionally very beautifiilly on sections paralell to the leaf sur- 

 face having passed just above a vascular bundle. One then 

 sees mesophyll -cells especially rich in alcaloid in a direction 

 corresponding to the direction taken by the vascnlar-bundle. 



On such happy sections one can judge of the direction 

 originally taken by the removed vascular -bundle, by the 

 large amount of alcaloid présent in thèse mesophyll cells. 

 Apparently the cells of the palissade- parenchyma contain 

 most of the alcaloid and frequently it is seen accumulated at 

 the sides of thèse cells bordering on the hypoderm (c. fig 

 99 Pl. VII). 



Etiolated leaves also contain alçaloid in ail parenchyma 

 cells frequently more than green leaves do (c. f. 100. Pl. VII). 



Thèse leaves had been developped under cover of a large 

 box from resting buds of an old Cinchona-trunk. Following 

 the method of Treub, small holes were made in them 

 by means of a hairbrush and the whole submersed in 

 the iodine solution. The brown precipitate of the alcaloid is 

 subsequently seen around thèse holes; (c. fig 108. Pl. VIII) 

 other leaves treated exactly in the same way, but previously 

 having been extracted with alcohol do not show this brown 

 precipitate, thus proving it to be due not to albuminous 

 substances but to alcaloid (c. fig 109. Pl. VIII). 



Is it legitimate to conclude from thèse experiments that 

 the alcaloid can be formed in the dark? By no means; 

 it can easily have been substracted by the leaves from the 

 large quantity présent in the bark, which bark originated 

 while the tree grew in the light, 



