80 USES OF THE 



proportion of iinicilage at the end of autumn 

 than in the early spring. If these substances 

 do not nourish the plant, they seem to be 

 of no use to it, whatever secondary purposes 

 they may answer in the schemes of Provi- 

 dence. The direct end, with respect to the 

 plant, of the finer secreted fluids of its fruit 

 can very well be perceived, as tempting the 

 appetite of animals, and occasioning, through 

 their means, the dispersion of the seeds ; and 

 the perfume of flowers may attract insects, 

 and so promote the fertilization of the seed, 

 as will be explained hereafter. 



After what has been said we need not waste 

 much time in considering the hypothesis, 

 advanced by some philosophers, that the 

 sap-vessels are veins and the returning ves- 

 sels arteries. This is so far correct, that, as 

 the chyle prepared by the digestive organs, 

 poured into the veins and mixed with the 

 blood, is, through the medium of the heart, 

 sent into the lungs to be acted upon by the 

 air; so the nutrimental juices of plants, taken 

 up from the earth, which has been called their 

 stomach, are carried by the sap-vessels into 

 the leaves, for similar purposes alread}" men- 



