6
the main, those of the London Clay and
Marine Alluvium. When virgin these colonise
initially with Bristly Ox-Tongue, Hawkweed
Ox-tongue, Prickly Lettuce and Melilot, and
mature with quite a varied but unspectacular
flora. In the north, however, we have the
distinctive verge floras of the chalk and the
chalky-boulder--clay, and the glacial sands.
Although similar, the flora of the chalky-
boulder-clay is distinctive in its species
assemblage from that of the chalk. Trag-
ically, it is the chalky-boulder-clay verges
in the districts of Uttlesford, Braintree and
Epping Forest that have suffered most from
dumping of decayed road metal.
Additionally, however, the chalky-boulder-
clay is a variable substrate and several
local flora types once existed:-
(i) For example, around Hatfield Broad Oak
and in local pockets around the Rodings and
the Easters, the chalky-boulder-clay once
supported the indicator species Greater
Knapweed, a typical plant of the chalk but
not in general of the chalky-boulder-clay.
In these pockets of what appear to be chalky-
boulder-clay enriched with extra chalk, the
following associated species were once
abundant and persistent: Rockrose, Marjoram,
Clustered Bellflower, Stemless Thistle, Milk
Vetch, Salad Burnet and Pyramidal Orchid.
In the same areas the Wayfaring Tree acted
as an indicator species in the hedgerows.
These apparently chalk enriched chalky
boulder-clay pockets are possibly derived
from the crumbled fragments of huge slabs of
chalk acquired by the ice sheets as they
moved across the chalk hills to the north-
west of Essex. This very local subtype of