PLANT NUTRITION. 23 
as it grows, as the feathers of a bird are removed during 
the moulting season. No such cap exists at the end of a 
branch or leaf. Again, while it is the office of a stem or 
branch to produce leaves or scales, which are the repre- 
sentatives of leaves, no root proper, as a rule, produces 
leaves or flowers. 
Botanists make a distinction between “true roots ”— 
which are the direct outgrowth from the original ‘ rad- 
icle ” of the germinating seedling, and, in fact constitute 
its direct continuation—and. “adventitious” roots, which 
spring from the stem and branches, and which are only 
indirectly derived from the primary root. For our pres- 
ent purpose the distinction is unimportant. 
The root of a plant and its branches have different 
forms and subserve different purposes. Whatever food is 
taken up from the soil is taken up by them. They act 
as stays and holdfasts, they serve as storehouses of nour- 
ishment. Their form varies according to their use, their 
needs, the competition with other roots, the conditions 
under which they have to grow, and other circumstances, 
not forgetting the heritage bequeathed to them by their 
predecessors from generation to generation, for, like all 
parts of the plant—like the plant itself—the root is the 
product of what has gone before, adapted and modified 
by the exigencies of the present. 
In this place we have to consider the roots chiefly in 
their character as absorbent organs. The one function 
common to all roots is absorption. They may have other 
offices to fulfil, and they have very varied forms; but 
when we come to consider the main function of the root, 
then we find simplicity and relative uniformity of struc- 
ture. The thick, woody limb of an elm root, as we see 
it exposed in a hedge-bank from which the soil has fallen, 
is no organ of absorption ; the thick “bulbs” (so-called) 
of a turnip or a beet, are not organs of absorption ; 
neither are these latter, any more than the tubers of po- 
