312 Transactions of the Canadian Instithtk. [Vol. VII. 



When CuSO^ is applied in solutions more dilute, as in strength 

 m/640, one finds it also producing a ring. This is easily recognized by 

 applying the solution to the under surface of a leaf of Primula stellata 

 (Hort.), which has a red colour. When the drop has remained for some 

 hours upon the leaf, one can see by the colour where the tissue has been 

 killed. The red colour disappears, and there appears a blue ring where 

 the tissue has shrunken below the general leaf surface. 



Strong acids and alkalies do not produce this ring because these 

 substances dissolve a way regularly through the tissue, permeating in all 

 directions, as is the case when these substances are applied to the cut 

 ends of the petioles. (See photographs 4, 5, 6). 



Series II. 



Experiments with solutions of CaHo(CO.;)j and Ca(OH)j upon 

 leaves of Begonia, Primula obconica, Primula stellata, Pelargonium and 

 Heliotro{)ium. 



When drops of each of these solutions were placed upon the upper 

 surface of these leaves, and allowed to evaporate in the open air, there 

 was a slight residue in each case; but if the leaf were placed in a flask 

 (Fig. 6), or if a detached leaf" were placed under a beaker to prevent too 

 rapid evaporation, the salts entirely disappeared. (The object of this 

 experiment was to test the effect of the soluble carbonate upon the 

 surface of the leaf). It took between tw^o and three days to absorb 

 completely the drop of solution. If the drop became dry in less than 

 twent}'-four hours there was a residue, showing that the loss by 

 evaporation was too rapid. Though the Ca(OH)... solution left upon 

 evaporation a small amount of crystalline matter, this was undoubtedly 

 not the hydroxide of lime but the carbonate, produced b}- the action of 

 CO-j upon the evaporating solution of the hydroxide. The deposit of 

 CaCOs then upon the leaf vanished upon the application of more water, 

 and especially so if the leaf were kept in a moist chamber as shown in 

 Fig. 6. An interesting fact to notice, was that if a leaf holding upon it 

 the residue from a drop of the solution of the bicarbonate which had 

 been allowed to evaporate rapidly, were placed as in Fig. 6, this white 

 residue vanished after a time. This was due to the moisture in the air 

 in the flask acting just as the water did upon the residue, causing it to 

 become again, in the presence of CO.., a solution of the bicarbonate, 

 which was then in this condition absorbed. This proves that a part of 

 the calcareous substances found upon the leaves of some plants, may be, 

 upon occasion, in the presence of moisture and CO-.., resorbed by the 

 plant. 



