1898] THE CHEMISTRY OF THE FOREST LEAF 183 
With reference to the scheme of the products of de-assimilation 
exhibited on the right-hand side of the aforedrawn table, it may be 
observed that a considerable experience in plant analysis is requisite 
in order to appreciate it thoroughly. Suppose, for instance, that 
we are determined to engage in a complete study of the chemistry 
of the forest leaf, we must commence with the earliest growth of the 
organ—in fact, we should commence with the winter buds, but at 
any rate we examine the young leaves just unfolded, and we, by 
appropriate methods of analysis, discover that one body seems 
almost universally present in them all, and that body is a tannoid 
compound (rutin or quercitrin), It is inevitably present because it 
is the first formed product of the chlorophyll (ie. the proteid) 
substance that has spent its energy, and lies in the position of a 
waste or excretum. But what then ensues ? 
The leaf progresses in growth. Oxidation more or less com- 
plete supervenes on every item of its tissues and contents which is 
not directly under the dominion of the reducing energy of the living 
and vigorous protoplasm. The tannoid compound aforesaid is 
gradually transformed -more or less completely into volatile oil and 
resin, or into tannin, but until the late autumn the change into the 
latter body is probably never entirely and absolutely accomplished. 
Practically in the majority of our forest trees there is no formation 
of essential oil in the leaves, but there is always apparently a 
residuary resinous body or a ‘ bitter principle’ extracted by benzene 
or alcohol, and there is invariably tannin, the quantity of which 
increases from spring till autumn, reaching its maximum about 
October or November. According to Kraus, there is generally 
twice as much in the October leaves as there is in the June leaves, 
That some such progressive change ensues as is here described, even 
supposing that a portion of the material formed is daily conducted 
away into the bark and wood, there can be no doubt whatever. 
On the whole, therefore, it may be admitted as established that, 
while the forest leaf is par excellence an organ of reduction so far as 
its purely and distinctively protoplasmic energy is concerned, yet at 
the same time very considerable and important oxidising processes 
take place among the lifeless ruins, so to speak, of its spent and 
exhausted activities. The bye-products, the waste of protein bodies 
are only partially and slowly excreted and cast off, an expulsion 
which dies gradually away in the old age and decrepitude of the 
organ when autumn comes upon the scene, and the reducing agencies of 
the protoplasm having been expended, the oxidising agencies of light 
and air enjoy unrestricted sway crowned by the golden and crimson 
glories of the autumn woodlands. P, Q. KEEGAN. 
PATTERDALE, NEAR PENRITH, WESTMORELAND. 
