195 
perfect development to plants when applied to the soil in which 
they live and grow. Plants, however, have always an abundance 
of oxygen surrounding them, which working upon the animal 
manures in the soil converts them into life-sustaining properties 
for plants. It is for this, as also for other reasons, that in the 
growing of crops rotation is beneficial. The plants that in their 
nature must remain in the same soil for years are subject to 
diseases not known or experienced by those that may be changed 
to different soil. 
In garden work the rose may be taken as a plant that is par- 
ticularly difficult to keep in satisfactory condition beyond a short 
period. ith the best of culture and with the most liberal and 
judicious fertilizing it is continually attacked by a number of 
aaa, which weaken and pee! destroy its power to een 
rong vigorous growth and to produce satisfactory flow 
ts will apply to other deaaie a s that must panies 
occupy the same soil for a number of years. 
I have seen the toxic extract taken from soil in which wheat 
had been grown for several years and applied to other soil in 
which wheat was sown. The young plants were struggling for 
life, wilting and dying, while seed that was put in new soil made 
strong and vigorous plants 
Apple orchards have been known to suddenly begin to decline 
without any well-known cause that was discoverable after thirty 
years of regular bearing. Orange trees, in some soils in California 
and in Florida, have been injured by the dying back of the ends. 
of the branches, causing thousands of dollars of loss to their 
There are without doubt conditions of the soil that 
a eee that are responsible for these tree diseases. 
Rotation wherever it may be followed is a good policy to adopt 
even with trees, where land may be available by planting new 
rchards on new soil and cutting out the old. Rotation in 
gardening, where it is possible to grow clover, peas, or vetch, 
will save crops from many kinds of diseases and from certain, 
insect pests. In intensive market gardening this is somewhat 
difficult on high-priced land. 
Thorough aération of the soil is essential. Oxygen is as nec. 
