3(5 PHILOSOPHICAL TRANSACTIONS. [aNNO 1672. 



the plant of its milky juice, as to kill it, though we have given it very many 

 incisions to that purpose. 



The substance of these veins seems to be as truly membranous, as the veins 

 of animals : a leaf will not give way and be extended, but the veins in a leaf, 

 if freed of all the woody fibres, may be stretched out to one third part at least, 

 and vigorously restore themselves again, just like a vein, gut, or any other 

 membranous ductus of an animal.- Again these membranous pipes are exceed- 

 ingly thin and transparent, because they suddenly disappear and subside after 

 their being exhausted of their juice ; and particularly in that we see the liquor, 

 they hold, quite through them, no otherwise than the blood through our 

 veins. 



Concerning the external figure of these veins and cavities, as well as other 

 accidents, we thought they would have been made more apparent to us, if it 

 were possible to coagulate the juice they hold, without much shrinking the 

 plant. We were in great hopes freezing would have effected this; which though 

 it did not succeed as we promised ourselves, in respect of the manifestation of 

 these accidents; yet it gave us some further light into the nature of the juice of 

 these veins. In the keenest frost we dissected the frozen leaves of the garden 

 spurge J and observed, that all the juice, besides that which these veins hold, 

 was indeed frozen into perfect hard ice, and to be expressed out in the figure of 

 the containing pores; but the milky juice was as liquid as ever, but not so 

 brisk as in open weather. 



As to the motion of these juices, these things are certain : 



1. That the milky juice always moves and springs briskly on the opening of 

 a vein; the limpid sap but at certain seasons, and as it were by accident. — 

 2. The venal juice has a manifest intestine motion, or fermentation, within it- 

 self. 



There seem to be in plants manifest acts of- sense. We instance in the sud- 

 den shrinking of some plants; the frequent closing and opening of flowers ; the 

 critical erecting of the heads of poppies from a pendulous posture, and parti- 

 cularly the vermicular motion of the veins when exposed to the air. Again, the 

 veins of plants may indeed be different, though at present we cannot tell where- 

 in they are so. The arteries within our heads arc hardly to be known by the 

 eye from the veins. Further there are natural and spontaneous excretions or 

 venting of superfluous moisture in plants, visible and constant in the crown im- 

 perial, rorella, pinguicula, &c. 



Lastly, we shall not omit to observe, that either we must take that away from 

 the other reasons given of the necessity of the circulation of the blood in ani- 

 mals, viz. the hindering of its breaking and clodding ; or we must grant the 



