In one year the fruit-crop in a given neighbourhood is a failure: in another year it gluts the market.

One explanation of this fact, which has its exact analogies in human life, will be given in the next paragraph.
(3) All forms of life are exposed to the attacks of enemies of various kinds.

Whether they shall beat off those attacks or succumb to them depends in large measure on the nature of the growth that they are making; and this again depends, largely if not wholly, on the nature of the general influences to which they have been exposed.
For many years I lived in a district in which hops were grown on a large scale; and I naturally took an interest in the staple industry of my adopted county.

I noticed that whenever (during the summer months) there came a spell of cold winds from the north-east--winds which tend to arrest plant-growth--the hop-bines were at once assailed by blight and other pests, and the safety of the growing crop was imperilled.

And I noticed further that when the wind got round to the south-west, and warm showers began to stimulate the growth of the flagging plants, the pests that had assailed them disappeared as if by magic, and the anxieties of the growers were relieved.