218 Biographical Memoir of Charles Bonnet. 



commonly reproduced a head before, and a tail behind. But a 

 sort of error of nature also sometimes manifested itself; the 

 middle piece produced two tails, and being unable to nourish 

 itself, was condemned to quick destruction. 



It seemed as if it were the destiny of Bonnet, that the half- 

 formed ideas, and uncompleted attempts of others, should fur- 

 nish him with the subjects of great discoveries, and beautiful 

 works; and, in fact, it is less by conceiving ingenious ideas than 

 by unremittingly pursuing their development, that the great 

 geniuses have gained their celebrity. The germ of the differen- 

 tial calculus is to be found in Barrow, and that of the central 

 forces in Huyghens ; yet Newton is not the less entitled to hold 

 the first rank in intellectual pre-eminence. 



Some experiments, undertaken with the view of making 

 shrubs vegetate without earth, and a conjecture of Calandrini's 

 regarding the design of the difference between the two surfaces 

 of the leaves of trees, led Bonnet to undertake his Traite de 

 TUsage des Feuilles^ one of the most important works on vege- 

 table physiology that the eighteenth century produced. 



He not only found existing in vegetables, in the highest de- 

 gree, that power of reproduction, by which, from any part of an 

 organised body, the whole may at all times be reproduced ; he 

 also observed and investigated that mutual action of the vege- 

 table and the surrounding elements, so well adjusted by nature, 

 that, in a multitude of circumstances, the plant would seem 

 to act for its preservation with sensibility and discernment. 

 Thus he saw the roots changing their direction, and stretch- 

 ing themselves out in quest of better nourishment ; the leaves 

 twisting themselves, when moisture was presented to them, in a 

 different direction from the ordinary Qne ; the branches straight- 

 ening or bending in various ways in search of purer or more 

 abundant air ; all the parts of the plants moving toward the light, 

 however narrow the apertures by which it was admitted. It 

 seemed as if the vegetable struggled with the observer in sa- 

 gacity and address ; and every time that the latter presented a 

 new allurement, or a new obstacle, he saw the plant bending it- 

 self in a different manner, and always assuming the position 

 most suitable to its welfare. While the leaves formed the prin- 

 cipal object of his reseachcs, Bonnet examined also the functions 



