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16 THE WORLD OF LIFE CHAP
Another point of some importance is the greater stability
in the flora of meadow as compared with that of pasture
land. In the former only one plant was an accidental
straggler, while in the latter there were 1 2, or two-thirds of
the peculiar species. These are mostly rare, and are very often
not truly British plants, so that they cannot be considered
as permanent pasture plants. The more stable meadow
flora is no doubt largely due to the fact that few of the late-
flowering plants are allowed to produce seed, and though
seed may be often introduced by birds or the wind, many
of these species soon die out It thus appears that though
pastures are actually richer in species than meadows, yet the
latter have a more permanent character, as almost all those
peculiar to pastures are comparatively rare and therefore
very liable to disappear through very slight changes of
conditions.
These various
here given, serve
facts, and many others
to show us how very
which cannot be
delicate are the
mutual relations and adjustments of plants to their total
environment. In proportion as that environment is subject
to change of any kind, some rare species die out, while others
become diminished in numbers. And what takes place in
single fields or other small areas, when closely studied, must
certainly occur on a much grander scale over the whole
earth, and especially in those countries and periods when
great changes of climate or of physical geography are taking
place. These detailed studies of " Meadow and Pasture
Analysis" as their author terms them thus demonstrate
on a very small scale that " struggle for existence " which, as
we shall see further on, is always present, acts in an almost
infinite number of ways, and is one of the most important
factors in the developmental changes of the World of Life.
We will now proceed to give some of the numerical facts of
plant distribution, in various areas small and large,
as well
as over the whole earth ; but it will be advisable first to
give a brief account of the way in which this is usually
dealt with by botanists.
Four years before the appearance of the Origin of
Species the great Swiss botanist, Alphonse De Candolle
published one of the most remarkable and interesting