G ART. 6. — Y. YEXDO : 



wall of the plant, and then inject the solution very slowly so as 

 to avoid excess. 



I experimented with Vicia Faha (exp. 79), applying the 

 aniline violet solution, and observed that the solution injected into 

 the medullary cavity was at first absorbed by the innermost layer 

 of pith-cells and was then carried by degrees through the pith-cells 

 toward the vascular bundles, so that it penetrated almost all the 

 pith and xylem parts. The walls of the xylem elements were 

 especially well tinged by it (see PI. II, Fig. 2), while the outer 

 tissues (i.e. ' cambium, phloem and primary cortex) remained entirely 

 free of it. This proves that the dye is carried to a distance only 

 through the xylem elements. 



In the case of lithium solutions applied, I invariably observed 

 that lithium was conducted through the cortical and medullary 

 parenchymatous tissues, but it is certain that the longitudinal 

 conduction is accomplished by the vascular bundles. We may 

 affirm from these facts that the parenchymatous cell is capable of 

 conducting certain injected substances, but its power of conduction 

 is feeble in comparison with that of conducting tissues proper. 



VI. Experiments in the moist chamber. 



I made some injection experiments in the moist chamber 

 with Vicia Faha. The results (see exp. 48a, 49) agreed in all 

 cases ; namely, the injected substance was carried not only upwards 

 but also downwards from the stem into which it was intro- 

 duced, and penetrated the branches attached to the stem at 

 tolerable distances below the point of injection. Lithium was detect- 

 ed, in this case, in the petioles and midribs of most of the leaves, 

 but never in the blades (small veins and mesophyU). In the 

 control plant (exp. 48b), however, it was present especially in the 



