334 Canadian Record of Science. 
they become yet more fully adapted to special requirements 
of the human system. Man is therefore dependent upon 
plants as the great preparers of his food, both directly and 
indirectly. 
With a more thorough knowledge of animal nutrition, 
we have come to recognize more generally than in the 
past, that the quality of the food supply effects a pronounced 
and most important influence upon both the physical and 
mental condition, and this influence must be exerted both 
directly and indirectly by the vegetation upon which man 
feeds. We are therefore brought to yet another principle, 
that any improvement in the character of the food supply, 
must operate advantageously for man, in a corresponding 
systematic improvement. 
But the great biological laws are not adapted with sole 
reference to particular forms of life—they admit of general 
application, and, as we learn from vegetable physiology, the 
character of the plant is subject to the influence of variable 
nutrition, in a manner quite parallel to that which we 
observe in animals. In this, therefore, we discover the 
possibility of a means of making plants more perfectly 
adapted to the highest physical wants of man, and any 
study which tends to promote this end, cannot fail to be of 
the greatest interest, bringing us, as it inevitably must, 
into closer relationships with those forms of life upon which 
we are so largely dependent for health, comfort, and enjoy- 
ment. 
The subject we have chosen for discussion this even- 
ing, is one of considerable magnitude—embracing con- 
siderations of the greatest practical and scientific interest— 
and could readily be dealt with from several points of view. 
Perhaps many would consider that a mere statement of the 
articles which constitute plant food, together with the fact 
that the earth and air are the great sources of supply, 
would fully exhaust the subject, but an enlarged view 
discloses the fact that the sources of food supply; the 
preparation of food for the use of the plant; the general 
process of waste and repair; the selective power of plants 
