12 



we see with the naked eye and call veins. In the center 

 of this tissue the vascular bundle or bundles are situated, 

 a mesophyll-sheath is absent of course, its function and 

 position is taken by the starch sheath. 



The epidermis cells of the leaf- veins contain no alcaloid, ail 

 parenchyma and collenchyma-ceïls do. Wether the celllayer 

 between phloëm and xylem in thèse thin veins contains 

 alcaloid or not is a question I do'nt dare to décide; I ne- 

 ver saw it there but it is so difficult to obtain sections of 

 thèse thin veins showing this layer clearly and intact that I 

 have not been able to make a large number of observations. 



Mesophyll-cells or cells belonging to the veins, contai- 

 ning oxalic acid, never contain alcaloid. 



5. The leafstalk. 



The leafstalk consists of a parenchyma, in the center 

 of which a ring of vascular-bundles showing some thick- 

 ning growth is seen. 



Inside of this ring we observe some other vascular bund- 

 les more or less irregularly distributed, while outside of 

 the vascular bundle at the upper side of the leafstalk usu- 

 ally a couple of small bundles are met with, one to the 

 right and one to the left (c. fig. 110 Pl. IX). The outside 

 of the leafstalk contains the epidermis and hairs; they con- 

 tain no alcaloid. Under the epidermis we find several layers 

 of collenchyma, which contain alcaloids (c. fig. 110, 111 

 Pl. IX). Proceeding towards the center we first meet with 

 several layers of large parenchyma-cells containing a large 

 quantity of alcaloids (fig. 110, 112. PI IX.), subsequently 

 with the starch-sheath with no alcaloids and finally with 

 the with pericycle containing alcaloid. 



The parenchyma situated between phloëm bundles con- 

 tains alcaloids. In the large cells like C. fig. 1 1 3 Pl. IX and fig. 



