XX INTRODUCTION. 



would not be right to omit altogether the name of 

 Grisenthwaite, whose book on the theory of Agricul- 

 ture (1819) is remarkable for the enlarged and ex- 

 tended views which it contains. It is true that the 

 author falls into many errors ; but, at the same time, 

 he was the first who entertained correct views of the 

 importance of nitrogen as an element of manure, and 

 of the necessity of supplying phosphates, as well as 

 substances containing nitrogen, to plants, like wheat, 

 chiefly cultivated for the sake of the azotized princi- 

 ple which renders them valuable as food. 



Intimately connected with the progress of Vege- 

 table Chemistry, is the study of Vegetable Physio- 

 logy: a knowledge of the one is essential to a perfect 

 comprehension of the other; for it is impossible well 

 to understand the chemical changes going on in the 

 organs of plants, if we are wholly ignorant of the 

 forms and structure of those organs; and, on the 

 other hand, the most complete knowledge of the 

 anatomy of vegetables could never lead any one to 

 sound and correct conclusions respecting the nutri- 

 tion of plants. It is rather to be regretted that 

 both Chemists and Physiologists have appeared to 

 avofd availing themselves of the advantages which 

 each might have derived by studying the results that 

 the others had obtained ; it is only by comparing 



