218 Botany

large groups of plants, whose leaves and stems may
differ enormously, the flowers are practically the same.
The kowhai flower is the same type as that of the pea,
but one plant is a shrubby tree while the other is a
herb. Compare again the hard leathery leaves of many
olearias with the soft spoon-shaped ones of the field
daisy. Yet the flower is practically the same in both.
The explanation is simple. It is through its vegetative
organs that a plant comes into relation with its
environment, and, therefore, in these, to meet changes
in its surroundings, modifications have arisen. The
reproductive organs are concerned always with the
same thing - the production of the seed, and as,
speaking generally, the same method will serve this
purpose in almost any environment, these organs have
undergone but little change.

It would seem from their close resemblance that
there are certain plants which at no very remote
period had a common ancestor. These belong to the
same species. There are certain groups of species
which from their general resemblance to each other
would appear at a period somewhat more remote, to
have also been derived from the same ancestor. These
groups of species form a genus. Genera may again be
grouped into natural orders, and, from the fact that the
different genera forming any one order show in their
broader features a close resemblance to one another, it
seems clear that these, too, at a period still more
remote, had a common origin. Natural orders or
families may again be arranged in tribes. Continuing
further, the groups become progressively larger till
finally, we have the following classification:-
1. Cryptogams produce no seeds, e.g., ferns
2. Phanerogams produce seeds
(a) Gymnospermas have naked ovules i.e., not
enclosed in an ovary, e.g., the pine.