FLORIDA .STATE HORTICULTURAL SOCIETY. 
tion, absorption, transpiration and 
growth. 
The plant breathes, that is, it uses 
oxygen and produces carbon dioxide as a 
by-product, as man and other animals do. 
It absorbs raw food materials from the 
soil and air, and manufactures them into 
food for the repair of old parts and the 
building up of new parts, this building up 
process being growth. It evaporates the 
water it does not need by the process 
called transpiration. These are the living 
processes in the plant, and it is the fail¬ 
ure or disturbance of one or more of 
these that produces that state of the plant 
called disease. 
WHAT are FAVORABLE GROWTH CONDI¬ 
TIONS? 
The conditions that are essential to the 
life of the plant may be classed as fol¬ 
lows : 
1. Proper food; which is obtained 
from the soil and air. 
2. Water; which is the carrier of the 
food materials and is a necessary part of 
the living substance. 
3. Proper temperature; which makes 
possible the vital activities that go on 
within the body of the plant. 
4. Proper light; that furnishes the 
plant with energy. 
5. Proper freedom from mechanical 
and other disturbances that might prevent 
the plant carrying on its activities. 
6. Proper amount of oxygen in the 
air surrounding the plant and in the air 
of the soil. 
These are the external conditions that 
are necessary for the maintenance of 
normal life processes within the plant. 
Any failure or disturbance of these fac¬ 
195 
tors affects the living processes of the 
plant, and may result in that state known 
as disease. Diseases that originate thus 
are known as Physiological Diseases. If 
the disease results primarily from a dis¬ 
turbance of the living processes by im¬ 
proper feeding it is known as a malnu- 
tritional disease. 
On the other hand, if the living pro¬ 
cesses are disturbed by living organisms, 
such as insects, fungi, or bacteria, the 
disease produced is generally spoken of 
as an insect, fungous or bacterial disease. 
I 
SOME DISEASES DUE TO MALNUTRITION. 
\ 
Although much has been said and 
written of malnutritional diseases, little 
has been done towards working out a 
thorough system of proof that these dis¬ 
eases are actually due to conditions of 
malnutrition. For ,this reason many 
diseases are classed as malnutritional dis¬ 
eases that are reallv due to other known 
* 
or unknown causes. 
Harter, in a bulletin on the control of 
malnutritional diseases (Virginia Truck 
Experiment Station, Bulletin No. 1) 
claims that the truck crops of that region, 
especially cabbage and spinach, are affect¬ 
ed with malnutritional diseases, the con¬ 
tributing causes for which are soil acidity, 
a deficiency of humus in the soil and the 
absence of desirable nitrifying bacteria. 
He states that remedial and preventive 
measures should consist of : (1) Limi¬ 
tation of the amounts of fertilizer used; 
(2) adjustment of the composition of 
the fertilizer to suit the crop require¬ 
ments; (3) the rational use of lime, and, 
(4) the maintenance of the organic mat¬ 
ter of the soil. 
