1898] THE CHEMISTRY OF THE FOREST LEAF 181 



produce carbohydrates, tannins, and extracts ; those that are soluble 

 in pentane tend to produce essences and oils." Hence supposing 

 that these two chlorophylls exist in different or varying proportions 

 in different species of plants, and practical analysis proves that they 

 do so, then we have a satisfactory explanation of the fact that some 

 plants are oil-producing, while others are starch-producing. It is 

 well known that the leaves of various species differ enormously in 

 their capacity for forming starch, and trees have actually been 

 classified by Fischer and Suroz into ' Fettbaume ' and ' Starkbaume.' 



There is, however, another view of the matter, viz., that pro- 

 pounded by Mr Mesnard, according to which, while the free fat oil, 

 carbohydrates, and the reserve albuminoids are products of assimila- 

 tion, the tannoid compounds, essences, resins, and tannin are products 

 of de-assimilation. All are products of chlorophyll, and all constitute 

 materials for the latex ; but the immediate origin of the fixed oil is, 

 if this version be correct, not the same as the immediate origin of 

 the essential oil ; whereas, according to Mr Etard, both of these 

 plant constituents proceed from the same kind of ' chlorophyll.' It 

 is hardly necessary to mention that the original doctrine formulated 

 by "Wiesner, and upheld by Fluckiger and Tschirsh and by many 

 other German chemists and physiologists, was that the essential oils 

 and resins are formed at the expense of starch or even of cellulose, 

 that in fact the resins and ethereal oils are the final products of a 

 series which begins with starch or glucose, and passes through tannin 

 as an intermediary (Franchimont had, however, contested this as to 

 resin) ; but according to Mr Mesnard the substances in question pro- 

 ceed from the transformation of the tannoid compounds produced by 

 chlorophyll. "The formation of the essential oil," he states, "is very 

 rapid, and is effected in a fashion almost immediate, while that of the 

 tannins and pigments recpuires a long exposure to light and air." 



Thus it will be seen that while many investigators, with some 

 honourable exceptions, were fumbling and bungling over the subject, 

 and allowing themselves to be misled and distracted by fanciful 

 formulas and mystical alchemy, the true scientific ideas and ex- 

 periments of a single Frenchman (with whom, however, Mr Blondel 

 may be associated) have thrown a powerful search-ray of light over 

 the hitherto dark and troubled waters. Personally I never could 

 swallow the doctrine that the tannins were derivatives of the carbo- 

 hydrates ; and notwithstanding Waage's elaborate formulary to prove 

 that phloroglucin is formed as the result of the splitting up of glucose, 

 I am more disposed to accept Nickel's view that it may be formed 

 by the withdrawal of water from inosite — a body whose reactions 

 seem to connect it to some extent with the proteids or albuminoids. 

 I am convinced that, save and except the processes connected directly 

 with assimilation, the other subsidiary and supplementary chemical 



