CLASSIFICATION 5 
the plant has taken the peculiar form of a root, part of a 
leaf, and part of a flower. Now those of the later type, 
with more variety, are considered the top form. To take 
another illustration, the lowest type might be represented 
by a mass of iron ore lying in a mine. This reaches a 
higher stage when it has been through the blast furnace, 
and part has become, say, pig iron, and part a bar of steel. 
And a higher stage still is reached when this bar of steel 
is broken up, tempered, and ground until its various parts 
have been developed into a box of surgical instruments, 
each perfect for its various use. So we can find examples 
among plants of every stage, from the single cell, or mass 
of uniform cells, up to the complicated structure of the 
clematis, with its branching roots, its twining stem, and 
its gorgeous purple flowers. 
Now the great business in which all plants are con- 
_ cerned is reproduction, the effort to ensure that their kind 
shall not die out, and the most important specialisation 
is devoted to that. This is the first point at which we 
look when arranging our groups, just as at many schools 
a boy’s place is chiefly settled by his proficiency in Latin 
and Greek. 
But when we have got our system of classification, 
there is a fresh danger against which we must guard. 
We must not look on these class boundaries as some- 
thing fixed by Nature which cannot be passed. On 
both sides we find cases which seem in part to belong 
to one class and in part to another, and various botanists, 
looking to one point or other, argue for raising or lower- 
ing the plant, just as masters may argue for moving up 
a boy or keeping him back according to his progress 
in their particular subject. Nevertheless, though there 
may be no real gap between the top boy in the upper 
