3 j2 Of Vegetation . 
no farther ufe, do perifh ; not only becaufe 
the now grown and more expanded leaves 
of the young plant or tree, do fo over-fha- 
dow the fupplemental leaves, that their for- 
mer more plentiful perfpiration is much a- 
bated ; and thereby alfo their power of at- 
tracting fap fails ; but alfo becaufe the fap is 
drawn from them by the leaves, and they be- 
ing thus deprived of nourilhmcnt, do perifh. 
As the tree advances in ftature, the firft, 
fecond, third, and fourth order of lateral 
branches fhoot out, each lower order being 
longer than thofe immediately above them ; 
not only on account of primogeniture, but 
alfo becaufe being mferted in larger parts of 
the trunk, and nearer the root, they have 
the advantage of being ferved with greater 
plenty of fap, whence arifes the beautiful 
parabolical figure of trees. 
But when trees ftand thick together in 
Woods or Groves, this their natural fhape 
is altered, becaufe the lower lateral branches 
being much fhaded, they can perfpire little j 
and therefore drawing little nourilhmcnt, 
they perilh ; but the top branches, being ex- 
pofed to a free drying air, they perfpire plen- 
tifully, and thereby drawing the fap to the 
top, they advance much in height : But vice 
verfa, 
