54 P. Q. KEEGAN [ JULY 



which split asunder internally, leaving a hollow space (resin-passage) 

 into which there flows the product of their spent and exhausted labour 

 (destructive metabolism), viz. the resin. Physiological operations of 

 this very pronounced and particular nature are rather rare in the woody 

 tissues of the stem and root of our Dicotyledons. Then again, we can 

 attest the curious transformations which the starch, fatty, and resinous 

 constituents of the wood of the Scotch Fir undergo at the different 

 seasons of the year. According to Fischer there is no starch at all in 

 the wood, pith, or bark during the winter ; and Jonssen asserts that at 

 this season the wood is entirely devoid of starch in all parts, but bears 

 a considerable quantity of fat-oil, finely distributed, which disappears 

 in April, while during the summer the wood is very poor in fatty 

 matter. The needle-shaped evergreen leaves, again, are divested of 

 starch in winter ; but about the 1st April, even while the chlorophyll 

 is still in the wintry condition, and although a low temperature and no 

 special sunlight may occur, these organs are found crammed full of 

 starch. So that here a very remarkable phenomenon is presented, viz. 

 a plenteous production of starch following quickly on the winter sleep, 

 and under conditions the very reverse of those which, in most of the 

 dicotyledons of our latitudes, are indispensable for accomplishing a 

 precisely similar effect. In fact, certain still undetermined causes, 

 operative after a kind of pre-ordained periodicity, seem to dominate the 

 physiological action of the protoplasm of these extraordinary foliar 

 organs. Coniferous leaves are always much poorer in nitrogenous and 

 in mineral constituents (ash) than those of deciduous trees, and the ash 

 generally contains larger amounts of magnesia, iron, and silica. On 

 the whole, it may be concluded, from a study of the character and 

 quantity of the chemical constituents, that the coniferous Gymnosperms 

 are subject to a fitful periodicity of physiological energy, interrupted 

 by corresponding and longer periods of repose akin to hibernation, which 

 permit of extensive accumulation of " dry substance " in the tissues 

 under the form, more especially of the products of de-assimilation 

 (tannoids, tannins, glucosides (coniferin), resins, waxes, and volatile 

 oil), while on the other hand the products of assimilation (starch, 

 fat-oil, and nitrogen-compounds) are relatively and absolutely scanty. 



Eeviewing now the more extensive and familiar field of the Dicoty- 

 ledons, we are impressed not only by the comparative chemical similarity 

 of certain of the woodland organisms, but also by the fact that a few 

 other groups stand forth singly and, as it were, with an isolated 

 heterogeneity as remarkable as it is apparently inexplicable. Peering 

 adown the wondrous vistas opened out to us by the resources and 

 appliances of chemistry, the squabbles of the " splitters " and " lumpers " 

 of the would-be systematic taxonomists seem fantastic and puerile ; the 

 hair-splitting agreements or otherwise in the essential or unessential 

 superficial characters of the organs of reproduction, etc., are liable to be 

 contemned or wholly ignored. We find that species of trees very 



