FOUNDERS OF NATURAL CLASSIFICATION 49 



by the leaves, they may not improbably be the materials 

 out of which the more subtle and refined principles of 

 vegetables are formed ... we may therefore reasonably 

 conclude, that one great use of leaves is ... to perform 

 in some measure the same office for the support of the 

 vegetable life, that the lungs of animals do for the 

 support of the animal life ; plants very probably drawing 

 thro' their leaves some part of their nourishment from 

 the air." That Hales studied the structure of the leaf 

 for himself and was not content simply to accept Grew's 

 word for the existence of stomata is manifest from his 

 remark : " I found little or no air came either from the 

 branches or leaves, except what lay in the furrows, and 

 in the innumerable little pores of the leaves, which are 

 plainly visible with the microscope." 



The notion that " plants very probably draw through 

 their leaves some part of their nourishment from the air " 

 is a very shrewd guess indeed, for you must recollect that 

 the composition of the air was not known until more 

 than sixty years afterwards, and only very imperfectly 

 even then. Leaves also absorbed light, according to 

 Hales, which " may contribute much to the refining of 

 the substances in the plant." Sachs in his account of 

 Hales's work holds that he followed Newton in believing 

 that light was actually a material substance. Hales 

 indeed quotes Newton as asking, " Are not gross bodies 

 and light convertible into one another ? and may not 

 bodies receive much of their activity from the particles 

 of light, which enter their composition ? The change 

 of bodies into light, and of light into bodies, is very 

 conformable to the course of nature, which seems delighted 

 with transmutations." 



Hales added nothing to our knowledge of the 

 physiology of reproduction. " If I may be allowed to 

 indulge conjecture," he begins, and then, very unlike 

 himself, he follows on with an extremely quaint hypo- 

 thesis in support of which he does not present any 



