\ 



^ 



.1. 



3. 



»nflu. 



pel. 



nd 



1 



-ie ex. 

 - Won, 



IS 



hlch i 

 •obabl 

 an that 

 al fur- 

 ^'ater is 

 :s, like 



le fame 

 ; lungs 



? trunk 

 well 



an 



» 



^ influ- 



robably 



he ligbt 



tion, as 



faces of 



bark oi 



heir ex- 



a 



reduce 

 ana caa 



r 



orwi- 



nu 



r 



fcula 

 the aif 

 feei^ 



s 



to 



tef 



on 



a 



crre 



9 



atef 



Sect. IV. L3. 



AND VEINS. 



4S 



greater expanfe of furface than In the lungs or gills of animals, which 

 well accounts for the exuberant extent of their foliage. 



In the lungs of animals the blood, after having been expofed to 

 the air in the extremities of the pulmonary artery, is changed in co- 

 lour from deep red to bright fcarlet, and is then colleaed and returned 

 by the pulmonary vein. So in the leaves of plants the vegetable 

 blood is rendered yellow in fome plants, as in celandine, chelido* 



in others, as in fig-leaves, ficus; and in fpurge, eu- 



pium ; 



white 



And the ftrudure 



phorbia ; and red in others, as in red beets, beta. 



of the leaf, as confining of arteries and veins to expofe the vegetable 



After having 



blood to the influence of the air, and to return it to the caudex of 

 the bud at the foot-ftalk of the leaf, beautifully became vifible by the 



> 



following experiment. 



A ftalk with the leaves and feed-veflels of large fpurge (euphorbia 

 heliofcopia) in June ijpi? had been feveral days placed in a decoc- 

 tion of madder, (rubia tin6loria) fo that the lower part of the ftem 

 and two of the inferior leaves were immerfed in it. 

 walhed the immerfed leaves in much clean water, I could readily 

 difcern the colour of the madder paffing along the middle rib of each 

 leaf. This red artery was beautifully vifible both in the under and 

 upper furface of the leaf; but on the upper fide many red branches 

 were feen going from it to the extremities of the leaf, which on the 

 other fide were not vifible except by looking through it againft the 



On this under fide a fyftem of branching veffels carrying a 

 pale milky fluid, were feen coming from the extremities of the leaf, 

 and covering the whole underfide of it, and joining into two large 

 veins, one on each fide of the red artery in the middle rib of the leaf, 

 and along with it defcending to the foot-fi:alk or petiole. On flitting 



light. 



one of thefe leaves with fcifi^ars, and having a common magnifying 

 lens ready, the milky 



blood was feen oozing out of the 



returning: 



vein on each fide of the red artery in the middle rib, but none of the 



red fluid from the artery. 



Ga 



All 



