488 Theory of the Nutrition [Bookiii. 



he did not distinguish, and of the position of leaves on the 

 stem. Bonnet's view of the functions of leaves, foolish as 

 it is, is historically important and therefore required to be 

 noticed, because it was really accepted during many years 

 in preference to the older and better ideas, and because it 

 shows how the power of judging of such matters had fallen 

 oft' since Malpighi's time. It appears to have been the praise 

 lavished on Bonnet by his contemporaries that made later 

 physiologists, who might have known better, take him for 

 an authority on the nutrition of plants. His experiments on 

 the growth of plants in another material than earth are if 

 possible more worthless than those with cut leaves. Here too 

 the idea was not his own ; for hearing that land-plants had 

 been grown in Berlin in moss instead of earth, he made 

 numerous experiments of the kind, and found that many 

 plants grow vigorously in this way, and bloom and bear seed. 

 But the theory of nutrition gained nothing by these experi- 

 ments, which were only a childish amusement. The few pages 

 which Malpighi wrote on the nutrition of plants are worth 

 more than all Bonnet's book on the use of leaves ; the former 

 by the help of some simple considerations and conclusions 

 from analogy really discovered the use of leaves ; Bonnet on 

 the faith of many unmeaning experiments ascribed to them 

 another function than the true one. 



We are unable to pass a much more favourable judgment on 

 the views respecting the nutrition of plants of another writer, 

 who otherwise did good service to vegetable physiology, and 

 to whom we shall return in our last chapter. It is true that 

 Du Hamel 1 , of whom we speak, was not an investigator of 



1 Henri Louis du Hamel du Monceau was born at Paris in 1700 and died 

 in 1 781. He had an estate in the Gatinais, and turned his studies in 

 physics, chemistry, zoology, and botany to account in the composition of a 

 number of treatises on agriculture, the management of woods and forests, 

 naval affairs, and fisheries. He was made Member of the Academy in 1728 



