9 
anatomical and physiological research we may discover why one 
variety dev&iops better in one climate than another and why it 
produces a fetter product in one place than another and eventually 
by careful Selection acclimatize a large series of plants which at 
present we can hardly induce to exist under special climatic condi- 
tions. This conquest over Mature will entail, however, a very large 
amount <bf research, and a very big cultivation area under the hands 
of scientific men whose tirae is exclusively employed in making such 
investigations. The possibilities of the results, however, are enor- 
mous, and will well repay the expenditure of time and money. 
H. N. R. 
JPLANT LIFE AND DISEASE. 
A plant is a breathing feeding object with many activities or 
functions ; it elaborates chemical compounds from the liquids it 
absorbs from the soil and the gases it assimilates from the air; it 
grows, reproduces its kind, and is sensitive to changes in its sur- 
roundings. If it cannot control its immediate conditions, it can to 
a great extent adapt itself to them. 
Growth is probably the most dominant phenomenon we associate 
with plants. It is affected by soil, water, air, light and heat. For 
each of these factors there is a certain range within which the 
functions of the plant regularly proceed. For each species of plant, 
for example, there is a certain temperature below which it will not 
grow, and likewise a definite temperature above which growth 
ceases. Between these two extremes and near the middle is a 
point — the optimum point — which is the most beneficial. There is 
a most advantageous strength (concentration) for each of the 
necessary salts in the soil, and optimum points for water and each 
of the other factors. If every factor is at its optimum the plant is 
in the best position for growth; most likely this condition is never 
realised in nature. 
Any prolonged derangement in the factors of growth usually 
results in a curtailment of function and this must be looked on as 
disease. From this point view a plant like the banana, which 
seldom produces seeds capable of germinating, is diseased. Disease 
is rather difficult to define, and for our purposes we may take it that 
a plant is diseased which is not growing in what we know from 
practice to be its normal manner. 
The causes of unhealthiness may be shortly put down as due to : 
( l ) Derangement of any or all of the factors of growth ; 
-l 2 ) Attacks of parasites (plant or animal). 
The question of the relation between the health of a plant and its 
immunity, or the contrary, from fungal attacks is decidedly not 
settled. It is held by many experts that fungal infection is due to 
