486 Theory of fhe Nutrition [BOOK in. 



who, relying on the same experiments as Reichel, supposed 

 that the vessels of the wood convey the ascending sap, a view 

 which made it impossible from the first to arrive at any real 

 understanding of the movement of the sap in plants provided 

 with organs of transpiration. But even the other great dis- 

 covery which we owe to Malpighi, that leaves are organs for 

 elaborating the food, was denied by Bonnet, who substituted 

 for it the utterly false view, that they chiefly serve to absorb 

 rain-water and dew. BONNET l , who had previously done good 

 service to insect-biology, and had discovered the asexual 

 propagation of aphides, having injured his eyes in these studies, 

 found an agreeable pastime in a variety of experiments on 

 plants. Much that he did was unimportant, yet he obtained 

 some results, which could afterwards be turned to account 

 by more competent persons, for the weakness of his own 

 judgment is shown even in his more serviceable observations, 

 such as those on the curvature of growing plants. We notice 

 the same defect in his observations on the part played by 

 leaves in the nutrition of the plant. It shows the character of 

 the time that a book like Bonnet's ' Recherches sur 1'usage 

 des feuilles des plantes,' a mere accumulation of undigested 

 facts, should have been generally considered an important 

 production. He tells us, that his attention was called by 

 Calandrini to the fact, that the structure of the under side 

 of leaves seems to show that they were intended to absorb 

 ' the dew that rises from the ground ' and introduce it into 

 the plant. Starting from this sensible suggestion, as he calls 

 it, he proceeded to make a variety of senseless experiments 



1 Charles Bonnet, bom at Geneva in 1720, sprang from a wealthy family, 

 and was intended for the profession of the law, but gave himself up from 

 an early age to scientific pursuits, and especially to zoology. He was after- 

 wards a member of the great council of Geneva, and wrote various treatises 

 on scientific subjects, psychology, and theology. He died on his property at 

 Genthod near Geneva in 1793. See the 'Biographic Universelle' and 

 Cams, ' Geschichte der Zoologie,' p. 536. 



