326 Transactions of the Canadian Institute. [Vol. VII. 



strengths of 5, 10, 20 per cent. It was found that caustic soda at 

 10 and 20 per cent, was too strong, producing holes in the leaves 

 after a few days. The strength of solution required to produce a spot 

 similar in appearance to the artificial tobacco spot, differed considerably 

 among the several plants tried, but the ten per cent, sodium carbonate 

 solution seemed to be the most generally successful. Twenty per 

 cent, sodium bicarbonate was used in the Nicotiana, but it was not 

 sufficiently strong to produce a spot and so no further attempt was 

 made with this substance. To each solution was added about one per 

 cent, by weight of lithium nitrate, for the purpose of utilizing the flame 

 test in determining whether the alkali was absorbed and transported 

 to other parts of the plant. It was found in all leaves that were tested 

 by means of the flame and the spectroscope, that the lithia had 

 penetrated to other parts of the same leaf, and also down to the 

 extreme end of the petiole. Lithia was not found in other leaves of 

 the plant, but it is inferred that the strength of the solution of lithia 

 was too low and that the instruments were not sufficiently accurate 

 or delicate to recognize it in such minute quantities, rather than there 

 was no transportation of lithia to other parts of the plant. Lithia 

 was found in few cases in the stem below the leaf, and in a very few 

 cases above the leaf node. Of course it might be objected that the 

 fact of the lithia being found transported did not prove that the caustic 

 soda was conveyed with it. This is a fair objection, because the 

 caustic soda might easily be all decomposed in acting chemically upon 

 the cutin, cell walls and cell contents. However, it is thought fair to 

 assume that at least a certain amount of the caustic soda or the sodium 

 carbonate, as the case may be, would accompany the lithia through 

 the plant tissue. Some of the caustic may be decomposed, as has 

 been proved by the writer in the case of the beautiful liquid colouring 

 matter in the epidermal cells of the red leaves of Ampelopsis in the 

 late autumn. Caustic soda turns the red liquid a deep blue, but this 

 blue rapidly disappears giving place to a greenish colour which soon 

 changes to a yellow. When an acid is now applied, there is no 

 reddening of the liquid, showing that some chemical change has gone 

 on upon the liquid contents by the action of the alkali. 



In all the leaves spotted artificially it was found that no spots or 

 mottling appeared except those spots plainly visible when the leaves 

 were lying upon a dark surface ; while in all the Sumatra leaves 

 available it was found upon examination with transmitted light that the 

 leaves were all mottled with darker coloured patches, spots and dots^ 

 not visible by reflected light. This might suggest the notion that the 



