PREFACE. 



EIGHTLY to understand what work is done by 

 living plants, and how it is effected, not only 

 requires a student to be a botanist in the ordinary 

 sense of the word, but necessitates that he should 

 also have a comprehensive knowledge of physics and 

 of chemistry. 



In few individuals can such an extensive know- 

 ledge now-a-days be expected. The practical cul- 

 tivator especially, harassed by the daily cares of his 

 occupation, is not able to master the endless details 

 of these sciences ; and yet experience shows the 

 increasing necessity for furnishing him with new 

 tools and new weapons to enable him to utilise the 

 resources of Nature, and to contend against adverse 

 circumstances. Such tools, such weapons are fur- 

 nished by the armoury of science. It is the object 

 of this Handbook to point out the nature of these 

 resources, and suggest the methods of utilising them. 

 Something will be gained if only a right appre- 



