VEGETABLE STRUCTURE. 
6i 
the thinneft pieces. They are reprefented in Fig. 33. at m m. In any 
of thefe which are cut entire, we may trace the origin and infertion, as 
well as the whole courfe. In that part of the thin piece which ha? been 
a portion of the body of the Root, if we have been fo happy as to cut 
thro’ one of the Clufters, we diftinguifli a fmall line between the Flefh 
and Pith, of a mixed dark and pale colour. This is reprefented at Letter 
n, and its termination at <?, fhews that it is a longitudinal view of or^e of 
thofe Clufiers j this feifllon having been made fo as to take the courfe of 
one of the twelve great Clufters juft within the furface, the variety of col- 
our is owing to the different coloured Veflels of which each cf thefe Cluf- 
ters is compofed. 
From one or other of the green Veftels of this Clufter arife all thofe 
white lines which pierce the fubftance of the interjacent Flefh, and make 
their way to the Clufters of the Fibre, where they form the vault or arch 
py at the head. Being white, it would be natural to imagine they arofe 
from the white Veflels of the Clufter ; but palpable obfervation fhews it is 
otherwife. I have fometimes thought I could diftinguifh a green thread in 
the middle of each. If it be fo, they have only thick white coats, but 
carry the rich green Juice of the Clufter. The Flefli of the Plant gives 
paflage to thofe Veflels, and as they proceed from the Clufters of the body 
toward thofe of the Fibre they unite two, or more, into one larger ; and 
in this enlarged form they are plainly inferted into the Clufters of the Fi- 
bre. Probably this is the origination of the Clufters in the Fibre, and 
in thefe arches at the top of the Fibre the Clufters properly begin, being 
produced by the united branches of thofe fmall white VefTels from the 
Clufters of the body, and naturally enough extending themfelves along 
each way, between the Flefh and Pith of the Fibre, till coming to the ex- 
tremity they return in an arch, and reach the head again, where they be- 
gan. This is the courfe of thofe Veflels in all the Fibres ; and the Letters 
e Cy f f \n Fig. 35 of this Plate, which reprefents the entire Plant diflTec- 
ted, divefted of its outer Rind, and with the inner feparated, and ready to 
be taken off, fhew part of the very fame conftrueftion with h i L m the 
Figure 33, only not enlarged enough to appear diftind:ly. 
CHAP. 
