



DISEASES 



\ 



and alfo on oth 



which grew under plum 



Sect. XlV. 3. 2. 



'ees, which were 



much infefted with an aphis of a greener colour. 



To prove beyond poffibility of error that this black matter was de- 

 jeded on the leaves below by the aphifes, which were walkino- with 

 their heads downwards on thofe above, I fewed flightly with a needle 

 and thread under feveral leaves a piece of writing paper about the fize 



of the leaf 



d obferved on th 



day that many black mark 



were diftinguifhable on the paper. 



On plum-trees and on many herbaceous plants innumerable aphifes 

 were feen on the upper tender part of the upright fhoots, adherino- 

 with their heads downwards ; and on the hanging fhoots with their 



heads upwards ; and iuferting their probofcis into the veffel 

 pofe, which contained the afcending fap-juice. 



Ifup 



But on th 



trees 



the mofl tender or uppermofl: parts of the young fhoots were covered 



with very numerous brill:! 



hich appeared to be an armour p 



pofely produced to defend them from thefe def^rudive infers 



d 



hen 

 leav 



they were principally found on the under furfaces of th 



e 



As the chyle of animals is mixed with the venous blood, and is imr 

 mediately projeded by the force of the heart into the pulmonary ar- 

 tery, at the extremities, of which it is principally converted into blood 



by 



pofure to th 



air 



fo in the vegetable fyR 



the fap-j 



mufl be mixed with the returning venous blood, and carried fo 



rds 



/ 



th 



m 



of the pulmonary artery of 



f, before it is 



ted into vegetable blood 



\ 



Thefe pulmonary arteries pafs along 

 the under furfaces of leaves, as the upper furfaces of them arc cover- 

 ed by the fine terminations of them on an air-membrane for the pur- 

 pofe of refpiration ; hence on thefe under furfaces of leaves the aphifes 

 adhere, and pierce the branches of the pulmonary arteries with their 

 probofcis {landing with their heads towards the flalk of the leaf, that 

 they may thus meet the flreams of chyle or fap-juice yet unchanged 



into- 



