INTRODUCTION. XXI 



togetlier the observations of both, that correct con- 

 clusions can be formed. The observations made by 

 the older physiologists, like those of their chemical 

 contemporaries, were mostly imperfect, and the deduc- 

 tions they formed, were, in consequence, very fre- 

 quently erroneous ; the modes of examination, and the 

 instruments which they employed, were far less per- 

 fect than those which have been used in more recent 

 times. Nevertheless, the observations recorded by 

 Grew, Malpighi, and Duhamel, are of considerable 

 value ; they may be said, indeed, to have laid the 

 foundation of Vegetable Physiology. As the study 

 of Botany itself advanced, greater care was bestowed 

 in examining the structure and anatomy of plants ; 

 and, from the labors of many zealous and careful 

 observers, there has resulted a tolerably complete 

 system of Vegetable Physiology. In recent years, 

 De Candolle, Brongniart, Decaisne, Dutrochet, and 

 Mirbel, in France; Link, Mohl, Meyen, and Schlei- 

 den, in Germany; Amici, in Italy; and Brown, 

 Griffiths, Henslow, Knight, and Lindley, in England, 

 have, besides many others, made valuable additions 

 to Vegetable Physiology. The relations of plants to 

 climate, and the influence of heat, light, and moist- 

 ure, have also been studied ; especially by Daniell 

 and Royle in our own country. 



