The Presidential Address, 21
occupied as weeds the manure and rubbish-heaps and waste
ground of civilisation.26 Such were probably the Mousetail
(Myosurus), the Mustards (Sinapis), the Penny-cress (Thlaspi
arvense), the Groundsels (Senecio), the Sow-thistles (Sonchus),
the Black Nightshade (Solanum nigrum), and probably the
Celandine (Chelidonium), the London Rocket (Sisymbrium irio),
and the Stinging Nettles (Urtica urens and U. dioica). The
only argument against the indigenous character of these
plants is that after the appearance of man they have chosen
to grow on the most richly manured land available to them,
thus frequenting his waste-heaps and cottage hedgerows.
With a greater rainfall and no artificial drainage far more
of the stiffer soils of Essex than at present must have been
marsh or peat-bog.27 The fall of a tree will clam a stream
and originate a pool of stagnant water, which may become
entirely blocked by Sphagnum, Osmunda, or Golden Saxifrage
(Chrysosplenium). On the peat thus forming Marsh-mari-
golds (Caltha), Sundews (Drosera), Pennywort (Hydrocotyle),
Whortleberries (Vaccinium), the Bog Pimpernel (Anagallis
tenella), the Spotted Orchis (Orchis maculata), the Ivy-leaved
Bellflower (Wahlenbergia hederacea), the Red-rattles (Pedicu-
26 See DeCandolle, op. cit., pp. 650, G52, sub Chelidonium and Sisymbrium
irio.
27 The following account of the Cambridgeshire Fen is suggestive with
reference to some parts of Essex :—"As the character of the Fen district
is very little known, it is well to remark that the peat is not formed of
Sphagnum, like that of the bogs, but consists chiefly of the remains of
various aquatic herbaceous plants. At the bottom there is a layer
formed mostly of the remains of the woody plants and trees which con-
stituted the forest which formerly covered the country. The remains of
oak, yew, hazel, and willow are found abundantly in some parts of the
Fens, and pine wood is plentiful in others. The wood of the larger trees
is often well preserved and turned quite black, but a few inches of the
surface have become soft and spongy. The latter is the condition of
most of the smaller branches and the lesser ligneous plants. The Rev.
Leonard Jenyns informs us that it is the opinion of the turf-cutters at
Isleham that, before the present more perfect drainage of the Fen, the
turf grew at the rate of about twenty inches in sixteen years. Now the
want of sufficient water has put an end to this restoration of the turf in
the places where it has been cut for fuel."—Professor Babington, 'Flora
of Cambridgeshire,' p. xviii.