68 
VEGETABLE STRUCTURE. 
femble it. We feek, by thefe experiments, the laws of Vegetation, and 
the Philofophy of Plants j and they are not to be determined from what 
we fee in a fingle fpecies. 
To render the obfervation eafier, it will be proper to view the others 
with the fame magnifying powers, and to take them as nearly as may 
be from the fame parts of the Plants ; therefore, as there is confiderable 
difference in the fliape of Roots, and as we fee the courfe of the Veffels 
is fomewhat altered by that flaape, altho’ their drudlure be the fame, it 
will be bed to fix upon the Bark of the Stalk in each kind, taking it off 
always near the bottom. 
As Roots are thicker, the mefiies of the reticular courfe of Veffels are 
wider, as in 36, 37, 38, and in confequence the crofs-bars become arched 
by the force which feparates the V’^effels thus far afunder in the fides of 
the mefiies ; but in Stalks, as there is one general form from which they 
never vary much, that is, a flender cylinder, the courfe of the Veffels 
will not be fubjedl to ihofe innumerable variations which the different forms 
of Roots occafion. 
It was convenient firft to trace the conftrudfion of this part, in pieces 
taken from the body of the Root, becaufe it is there original, and the 
V’’effels, and their mouths, are both much larger than in any part above 
ground : but there is equal reafon for chufing the Bark of the Stalk for the 
objedt of comparlfon with that of other Plants, becaufe being free from 
thofe accidental variations which the fhape of the root gives, there will be 
no confufion in the enquiry j no accidental differences will be feen, and 
we fhall therefore puiTue more diftindtly the real variations or fimilitude. 
The piece of the outer Bark of the Flowering Stalk of Hellebore, 41, 
fiiews that confirudtion and difpofition of the Veffels, with which we are 
to compare thofe of others. The Veffels in this run nearly flrait, at to- 
lerably regular diftances ; and the bars by which they inofculate one with 
another, are placed at a confiderable difiancc, and difpofed nearly at right 
angles with the others. The fringed mouths in thefe are very minute, 
and are placed principally at the joints, and in the crofs-bars. 
In the outer Bark of the Anemone the Vefiels are much thicker, and 
the crofs-bars very flender j in thefe the mouths arc placed at fmall dif- 
tances all along the inner furface of the longitudinal Veffels, and the crofs- 
bars ferve merely for communication between one of the afcending Vef- 
fels and another j they are fo (lender that they appear as mere Fibres and 
their cavities are inconceivably fmall. 
The 
