BIRCH GROVES OF EPPING FOREST. 75
of a birch grove completely carpeted during the winter months
with birch fruits and scales; they are by no means all blown
away. A gentle breeze passing through the ripe catkins is
sufficient to bring down the fruits. In January of the present
year they were seen on the ground at High Beach equalling at
least 5 to the square inch, which means 20,072,448,000 to the
square mile.
From what has already been stated it is quite obvious that
the number of seeds that successfully germinate is a very small
percentage of the number shed. A large proportion of the
seeds are not set and others are attacked by an insect that
deposits an egg within the young seed.5
A bed of moss is a suitable nidus for birch seeds to ger-
5 A dipterous fly, Oligotropus Betulae, attacks the catkins and seeds of the birch, and is in
its turn parasitised by a minute Hymenopteron belonging to the Chalcididae: specimens of both
these were bred in the Club's Museum from birch seeds from Epping Forest. According to Mr.
Blair, of the British Museum (Natural History), the Oligotropus has apparently not been re-
corded hitherto from Britain.—Ed.