26 H. G. SMITH. 
for instance, in small amounts in all the species of Oallitris 
and Kucalyptus growing in Australia, does not suggest 
that this element, at all events, is there by accident. If 
it were possible to follow this substance through all its 
ramifications in the tree it would probably be found to be 
in unstable association, and a necessary factor in the pro- 
duction of more stable substances, if not even largely 
responsible for the very existence of the plant itself, 
Professor Bertrand, in an address before the International 
Congress of Applied Chemistry, discussed the role played by 
traces only of chemical substances in biological chemistry. 
He pointed out that besides the three or four elements 
which it is generally recognised go to form plant substances,. 
there may be more than thirty other elements which may 
be detected in the plant in minute proportions, even to less. 
than one 100,000th of the plant’s weight, but which play 
an important part in the life of the plant and in its develop- 
ment. As will be shown later with certain of the Hucalypts. 
this minuteness may extend to less than one in a million 
parts of anhydrous timber. 
It may be that the correct application of these minute 
quantities of mineral substances, which probably act as 
catalysts, would result in enormous economic advantages 
in production, and lead to increased formation in the plant 
of what at present are but rare and costly commodities. 
The discovery of radium and its influences on plant growth 
has stimulated enquiry in corresponding directions, and 
Stocklasa has shown that both uranium and lead nitrates, 
in small proportions, definitely augment vegetable growth 
and production, although having less influence than radium 
itself. The literature in regard to this subject of inorganic 
influence on plants is now somewhat extensive, from a 
perusal of which it may be seen that a considerable number 
of the so-called rarer elements have at one time or another 
