322 Transactions ok the Canadian Institi tk. [Vol. VII. 



leaves, etc., were impregnated with certain substances tlie burning 

 quality was affected, — that phosphates and chlorides were detrimental 

 to, and that potassium nitrate aided in the burning. 



Adolph Mayer, writing upon combustibility, shows that potassium 

 carbonate was favourable to burning, and that chlorine compounds were 

 unfavourable. If leaves lack potash they have a "poor burn." He 

 shows also that these qualities may be produced in two ways, (i) by 

 using certain fertilizers, chiefly Chili saltpetre, (2) by impregnating the 

 cured leaf with this substance. By saturating tobacco having a " poor 

 burn " with a solution of potassium nitrate or potassium acetate he 

 caused the leaf to have what he called a "good burn." He also found 

 that when Chili saltpetre was used abundantly as a fertilizer for the 

 tobacco crop, a spotting was often produced in the cured leaf, because, 

 as he states, the leaves cured more slowly and unevenly ; and that when 

 the leaves were simply dried instead of cured, a greenish mottled 

 appearance was liable to result. 



In Griffon's researches (1900, p. i), he proves that nitrates in the soil 

 and in nutrient solutions add greenness to the leaves of plants, and that 

 salts of copper in minute quantities augment the dimensions of the 

 chloroplasts and the intensity of the colour, though it may kill the roots. 

 Sodium chloride is uniformly unfavourable, and an excess of lime causes 

 a paleness and a consequent lessening of assimilatory power. The 

 palisade tissue, chiefly, is affected (by the abnormal conditions), both as 

 to the dimensions of the chloroplasts and the cells themselves, and in 

 the colouration of the chloroplast. The writer has found, when decoctions 

 are made of the leaves of several kinds of cured tobacco, by steeping 

 them in distilled water for ten or twelve hours, that these decoctions, to 

 a litmus indicator, show a decided acid reaction in most cases. The 

 litmus paper used was purposely made slightly alkaline in order to 

 insure evenness in quality of the paper and to emphasize strongly the 

 experiment. One can secure litmus paper of an even quality by 

 steeping the paper to be used, in distilled water to which a very few 

 drops of ammonia have been added. The Virginia leaf changed the 

 colour of the deep blue litmus paper in two minutes, the Sumatra leaf 

 \-aV\w<^ five minutes, the artificially spotted leaf ten minutes and the leaf 

 artificially spotted then dried, not cured, taking three and a-half 

 hours. 



Mr. A. J. Ewart has shown (1896), that plants tend to neutralize both 

 acids and alkalies, and that so long as the substance in which he placed 



