DISTRIBUTION OF ANIMALS AND PLANTS IN FELSTEAD, ESSEX. 199
but the rest are sporadic. Some two or three are remnants of an
ancient woodland flora, and are consequently confined to narrow
limits. Among the sporadic species is the Bee Orchis. As I have
never found this except on very chalky Boulder-clay, I infer that its
distribution in Essex is confined to the limits of that deposit or to the
districts in which the chalk outcrops. This appears to be a case in
which geological causes have solely controlled the distribution of a
plant. It would be interesting to know if the Bee Orchis occurs
away from either of these deposits in Essex. According to the
localities given in Gibson's "Flora of Essex," it does not. The Fly
Orchis appears to stand on the same footing.
The occurrence of sporadic forms does not seem to be in any
way connected with the advent or departure, or rather the local
increase or decay, of species. It rather seems to be connected with
those conditions for the preservation of the germs of plants which
are often found in the earth, but which are said to be hard to imitate
artificially. The subject has been so often discussed since the days
of Gilbert White, that some apology is almost necessary for its intro-
duction. The tendency is, I believe, to discredit the statements of
many observers. Of one remarkable case I was an eye-witness.
From thirty-five to forty years ago the Bee Orchis grew by a wood-
side here in quantities. There is good evidence of this. For about
twenty years afterwards no plant was known to have occurred there,
nor within one or two miles of the spot, although diligently sought
for during most of those years. A few square yards of turf were
then removed, and the following year five plants of the Bee Orchis
came up and flowered at that place. It would seem that this case is
very similar to some quoted by Gilbert White.
Something which may be likened to the rotation of crops also
appears to be bound up in this question of the preservation of germs.
A pond containing a little water produced in abundance Potamogeton
for two or three years. This died out, and the naked Horse-tail
(Equisetum) reigned in its place and grew very vigorously, although
no other plants of the species occurred for a mile at least. After a
few years the Equisetum was succeeded by Sedges, which are now
failing. It seems almost certain that the germs were already there,
and only awaited their opportunity for sprouting.
The dispersal of the seeds of plants is due to various agencies—
wind, water, animals, etc., and is therefore an uncertain and incalcu-
lable element. But although these agencies may be ever at hand,