INTRODUCTION. 



tainly added to the produce of our horticulture and our 

 farming ; but we little know, while we are acting thus, that 

 we are sacrificing the guardians of our vegetable wealth, and 

 giving protection and scope to its destroyers. The whole of 

 nature is so replenished with the germs of small life, in a 

 condition ready to be developed the instant that the state of 

 heat and moisture accords with their development, that a 

 means for preventing their extraordinary increase, more 

 efficient both in itself and in its application than anything 

 of human contrivance, is absolutely requisite, in order to 

 preserve that relative balance which is essential for main- 

 taining the system of nature, and which no part of that 

 system is without. 



Every bud, every crevice in bark, very many roots, all the 

 pools and slow streams, and all animal and vegetable matters 

 in a state of decay, are full of the rudiments of small animals 

 in some state or other, and those rudiments are awakened so 

 easily, and by causes so little open to common observation, 

 that, if there were not some counteracting power, our gardens 

 might, in the course of a single season, be left without a 

 blossom, our forests without a leaf, and our fields without* a 

 blade of grass, a spike of corn, or an esculent root. If this 

 once took place, vegetation would be gone, save the poison- 

 ous fungi which might be nourished by the remains of the 

 destroyers. 



We have partial experience of this almost every season. 

 When the wind of the early year is soft, and the showers are 

 genial, the leaves and the blossoms are perfect in their forms, 

 and rich in their colours ; they are also cool in their tempe- 

 rature, and their sap is astringent. If this state of things 

 continues, the year is one of abundance ; but if, in the midst 

 of the verdure, the east wind should dry the surface of the 

 leaves, and the unclouded sun, co-operating with the wind, at 

 the same time raise them to a certain temperature, the juice 

 which is in them would become saccharine, as it does in 



