70 HISTORY OF BOTANY 



Calandrini, of Geneva, viz. that the under side of the leaf 

 absorbed the dew that rose (!) from the soil. Bonnet's 

 rank among the pioneers in plant physiology cannot be 

 more tersely expressed than in Hansen's scathing words : 

 " Whenever a history of false prophets in science comes 

 to be written then Bonnet will come into his own, for he 

 will be found marching in the very front rank." 



The only other name I need mention is that of Du 

 Hamel, who, in 1758, compiled an account taken from 

 the works of Malpighi, Mariotte, Hales, Bonnet, and 

 others. When I tell you that he thought the soil was a 

 sort of digestive organ which prepared the food that the 

 root absorbed, and that the leaves were suction pumps 

 for drawing it up, I think you will admit that Du Hamel's 

 contributions to the theory of nutrition are not likely to 

 repay much expenditure of time on their study. In one 

 direction, however, viz. the movements of plant organs, 

 Du Hamel seems to have made some observations worth 

 recording. Ray had noticed the periodic movements of 

 leaves of Leguminosae and the heliotropic curvatures of 

 shoots, and attributed them to changes in temperature. 

 Dodart attempted to explain geotropic curvature of roots 

 and apogeotropic curvature of stems by assuming the 

 contractility of fibres on the damper side of the root and 

 the drier side of the stem. Du Hamel, on the other 

 hand, asserted correctly that heliotropic curvature was 

 dependent on light, but that movements of Mimosa 

 leaves were independent of it seeing that they took place 

 in darkness also. Evidently he did not continue his 

 experiments for a long enough period. He also extended 

 Hales's pioneer observations on growth, confirming that 

 acute observer's statement that growth in length is 

 confined to the apical region of the root. 



Although no connected research was carried out 

 during the eighteenth century on plant movements in 

 general, a considerable number of scattered observations 

 had been recorded, such as the spontaneous or contact 



