DEVELOPMENT. 67 
larged, and displace the soil around them. They 
then, in turn, give origin to other branches, 
which, in like manner, elongate, increase in size, 
and ramify. This process continuing, there is 
formed, with greater or less rapidity, according 
to the species of plant, and its power of growth, 
an extensive ramification; until, in the case of a 
full-grown Tree, we have a network of roots ex- 
tending oftentimes, both vertically and horizon- 
tally, to a considerable distance from the bole of 
the stem, the primary, or first formed root- 
branches, frequently acquiring an enormous size, 
and making an appearance when, as is often the 
case, they are seen above the surface of the 
ground, like large branches of the trunk. From 
these enormous root-branches there is a regular 
gradation downwards in size, the ultimate filaments 
being amongst the most minute of threads. The 
upheaving power of the roots of large Trees is 
enormous: for, as the roots grow in size, they 
become hardened by the transformation of their 
soft tissue into the thickened and consolidated 
tissue which we call wood; and these woody 
