INTRODUCTION.

XIII

Chemistry, is the study of Vegetable Physiology; aknowledge of the one is essential to a perfect compre-hension of the other, for it is impossible well to under-stand the chemical changes going on in the organs ofplants, if we are wholly ignorant of the forms andstructure of their organs; and, on the other hand, themost complete knowledge of the anatomy of vegetables,could never lead any one to sound and correct conclu-sions respecting the nutrition of plants. It is rather to beregretted that both Chemists and Physiologists have ap-peared to avoid availing themselves of the advantageswhich both might have derived by studying the resultswhich the others had obtained; it is only by comparingtogether the observations of both that correct conclu-sions can be formed. The observations made by theolder physiologists, like those of their chemical contem-poraries, were mostly imperfect, and the deductions theyformed were, in consequence, very frequently erroneous;the modes of examination, and the instruments whichthey employed, were far less perfect than those whichhave been used in more recent times. Nevertheless, theobservations recorded by Grew, Malpighi , and Duhamel,are of considerable value; they may be said indeed to havelaid the foundation of Vegetable Physiology. As thestudy of Botany itself advanced, greater care was be-