120
THE ESSEX NATURALIST.
two families are separated from the others by having ectognathus
mouth-parts. These two families are scaled, possess the full
number of abdominal segments, compound eyes and have two
or three long tail-appendages. Only some half-dozen species of
Machilidae occur in England, one of which Pracmachilis hybernica
should occur in Epping Forest. The Lepismatidae have only
two British species, one, the common Lepisma saccharina Linn.,
if looked for may be found in houses.
The Campodidae are white, elongated insects with many jointed
antennae and two long tail appendages or cerci. Some eighteen
species are known from England and several will probably be
found to occur in the Epping district. So far, however, only
one, Campodea staphylinus (West) Bagnall nee. Silv., has been
found. This occurred in small numbers under loose bark.
NOTES ON HETEROPHYLLY.
By G. Lister, F.L.S.
(With 1 Plate).
[Read 31st January, 1931.]
HETEROPHYLLY is a term used to denote the occurrence
of two or more different forms of leaf on one individual
plant.
It is wonderful how constant and characteristic are the
shapes of the leaves of each species of plant, although it is such a
commonplace that one rarely gives it a thought. Then again,
when one's attention has been drawn to it, how many plants
there are that habitually show a variety of foliage in one indi-
vidual. In the following notes I have put together examples
of different types of heterophylly which I have met with in recent
years, while weeding and gardening, or while studying our wild
flora. There is nothing new about the observations mentioned,
but some of the facts are rarely referred to in systematic
books, though they will probably be familiar to some of my
audience.
HETEROPHYLLY IN SEEDLING HERBS.
An example of this occurs in our common Shepherd's Purse,
Capsella Bursa-Pastoris. On cultivated soil, at this season of
the year, hosts of the rosette-like seedlings may be found
scattered over the ground, some having almost entire leaves,