YOL. VI.] PHILOSOPHICAL TRANSACTIONS. 669 



breadth, because the course of the juice in these vessels is by the length of the 

 plant; as I have sometimes very plainly traced in the pith of a dried fennel- 

 stalk, following them by dissection quite through the length of the pith. It 

 remains that, if pores, they are of those pores of the cortical body, that are sup- 

 posed to be extended by the length thereof; which yet seems, to me at least, 

 not enough, but we think them vessels invested with their own proper mem- 

 branes, analogous to the veins of our human body ; for these reasons : 1 . Be- 

 cause they are to be found in the pith, and sometimes in the cortical body of a 

 plant, not included within the common tunicle of any fibres, as is above noted: 

 (that fibres or the seminal root are clothed, is most plain in some plants, as m 

 fern and geranium batrachoides, the fibres of the former are coated, at least in 

 some parts of the plant, with a black skin, in the latter likewise with a red one:) 

 And in these cases had they not, I say, their own proper membranes, we see no 

 cause why the very porous and spongy body of the pith and cortex should not be 

 in all places filled alike with the juice, and not rise, as most plainly it does, in 

 a few determinate and set places only, that is, according to the position and 

 order of these vessels. — 2. Again the experiment I made, which you were 

 pleased to publish,* concerning the effect of a ligature on cataputia minor LobeL 

 viz. the sudden springing of the milky juice out of infinite pores besides the in- 

 cision ; the cause of which phenomenon I take to be, the dissected veins im- 

 petuously discharging themselves of part of their juice within the porous 

 parenchyma of the bark ; whence it is probable, that if there was no coated 

 vessel to hold this milky juice, we might well expect its springing upon the bare 

 ligature, as when we squeeze a wet sponge ; the external cuticle of the plant, 

 as this experiment shows, being actually perforated. 



In the next place, it is very probable that these vessels are in all plants what- 

 soever. For as it is probable of all the other substantial parts of plants,, that 

 they are actually in, and common to all plants, though specified by divers ac» 

 cidents in figure and texture ; so of these veins, which, though they be dis- 

 cernible mostly in those plants where they hold discoloured juices, yet we may 

 very probably think that they are wanting, where the eye finds not that assist- 

 ance in the challenging of them. As in these very plants where they are least 

 visible, there is yet a time when they are, if not in all, yet in some parts of these 

 plants, plain enough to the naked eye : The tender shoots of the greater and 

 lesser maple, in May, are full of a milky juice, viz. the known liquor of these 

 veins. Again to this purpose, if you apply a clean knife blade to a transverse cut 

 of the like shoots of elder, the gummy liquor of these veins will be drawn forth 



* See Number 70. 



