58 P. Q. KEEGAN [july 



which is destroyed by acids and increased by a trace of alkali. Fraxin 

 is a colourless crystalline glucoside of a feebly bitter taste, and seems 

 to be related to quinic acid or hydroquinone. The tannin of the Ash 

 is totally different from that of any of our native or denizen trees : it 

 is distinctly iron -greening, is not a glucoside, does not yield anhydrides 

 by the action of acids, but only by heating dry or by repeated evapora- 

 tion of its solution, when brown substances (recalling the dun shade of 

 the autumn leaves) are produced, and finally on potass-fusion it yields 

 protocatechuic acid but no phloroglucin. In fact, it is doubtful if any 

 constituent with a phloroglucin nucleus occurs in the entire organism; 

 for the quercetin found in the leaves from birth till late in August 

 shows at all times reactions more like those of a tannin than of a 

 mere tannoid compound. The leaves may be regarded as among the 

 wonders of British botanical chemistry. Eeplete with chlorophyll and 

 carotin, they contain much starch, fat, and resin, and from 6 to 9 per 

 cent mineral matters (ash), but they are specially distinguished by the 

 number and variety of decomposition products, which constitute an 

 exceptionally high non-nitrogenous extract consisting of quercetin, 

 tannin, inosite, mannite, glucose, gum, mucilage, malic acid and its calcium 

 salt in astonishingly large quantity. On the whole, we see that the 

 small and short-lived leaves of the Ash are extraordinarily active, and 

 we are impressed by the apparent contradiction between the enormous 

 percentage of mineral matters indicative of an intense transpiration and 

 the small number (150) of stomata per square millimetre of epidermis ; 

 the carbohydrates produced on assimilation are largely oxidised to 

 acids, but the chlorophyllian protoplasm itself in its descent on 

 exhaustion stands hesitating, so to speak, on the first round of the 

 ladder, the not very oxidised tannoids. 



Much instruction and edification would doubtless be gained by a 

 specific recital and description of the chemical constituents of the 

 arborescent Eosaceae, e.g. the wild cherry, the rowan tree, etc., with 

 their wondrous plethora of products of de-assimilation and of carbo- 

 hydrate degradation ; but as these are assuredly scattered and not 

 forested, I now pass on to a tree which, although not a sterling native, 

 has yet been frequently artificially planted in our parks and groves 

 on such a plan and with such effect that the serried outskirts of a 

 dense forest — vast columns upholding a dome of leaves and flecked 

 with white clusters of blossoms, have at least been suggested. This 

 is the beautiful Horse-Chestnut (Aesmlus Hippocastanum), and truly 

 there is something very satisfactory in the chemical distinguishment 

 and examination of so many constituents that are comparatively simple 

 and afford atomic groups more or less harmoniously proportionate. 

 The well-known tannin, C 26 H 24 12 , for instance, has a number of atoms 

 of hydrogen nearly equal to those of carbon, and exactly double those 

 of oxygen ; hence its reactions come out very decisively, the deficiency 

 in carbon being a great help towards the ready production of a series 



