8 HISTORICAL INTRODUCTION. 



a plant of barley consisting of 249 stalks, springing 

 from one root or grain of barley ; in which they 

 counted above 18,000 grains or seeds of barley. But 

 do you think that it is barely the salt-peter, imbibed 

 into the seed or root, which causeth this fertility ? 

 no : that would be soon exhausted and could not 

 furnish matter to so vast a progeny. The salt-peter 

 there is like a magnet, which attracts a like salt 

 which fecundates the air, and gave cause to the 

 Cosmopolite to say there is in the air a hidden food 

 of life." 1 



DuJiamel and Hales. 



The names of the French writer, Duhamel, and of the 

 English, Stephen Hales, may be mentioned in passing 

 as authors of works bearing on the question of veg- 

 etable physiology. Both of these writers flourished 

 about the middle of the eighteenth century. The 

 writings of the former contained much valuable in- 

 formation on the effects of grafting, motion of sap, and 

 influence of light on vegetable growth, and also the 

 results of experiments which the author had carried 

 out on the influence of treating plants with certain 

 substances. ' Statical Essays, containing Vegetable 

 Staticks ; or an Account of some Statical Experiments 

 on the Sap of Vegetables, by Stephen Hales, D.D.' (2 



1 He then goes on to relate a number of experiments by Cornelius 

 Drebel and Albertus Magnus, showing the refreshing power of this 

 balsam, and then those of Quercitan with roses and other flowers, 

 and his own with nettles. 



