170
THE ESSEX NATURALIST
METHODS
From an examination of the previously prepared distribution map.
a transect line was planned, which would pass through as many features
as possible. This line starts at the north side of the common, and
passes through a Betuletum on sand, into a Quercetum on sand fol-
lowed by clay, and touches a small area of Carpinetum, also on clay,
before terminating at the opposite side. The transect line consists of a
number of "legs", the bearings of which were carefully plotted so that
the line could be followed accurately in the field.
It was not intended to record every tree along the transect line;
instead, the nearest tree on either side of the line at every five-foot
interval was taken and identified. For convenience, the transect was
made in 100-ft. sections, a steel tape being laid down on the correct
compass bearing. There were thus twenty records in each hundred-foot
section.
Identification of all trees was made from examination of the leaves
only. As this work is concerned chiefly with the distribution of the
species of oak, the less frequent birches were recorded only as Betula
alba, or Betula spp. Two species of oak were recognised: Quercus
robur, the leaves being very nearly sessile and having small auricles
where the blade joins the petiole; Q. petraea, the leaves being long-
stalked and the blade narrowing gradually into the petiole. Specimens
having intermediate characters were grouped as Quercus hybrids. In
all, 480 trees were identified in a transect line 2,400-ft. long.
At the end of each 100-ft. section, a soil sample was taken at a depth
of 22-ins., using a simple auger. The samples were analysed on the
spot by a visual examination and by the 'feel' of the soil when moistened
and rolled between the fingers. Three soil categories were recognised:
Sandy, the sample having obvious sand grains, and being friable; Sand-
with-Clay, there being less sand, and the sample feeling smoother and
tending to form filaments when rolled; Clay, without sand grains, and
the sample forming filaments easily when rolled.
At the same time, the general slope of each 100-ft. section was
recorded, so that a profile of the transect line could be drawn later.
ANALYSIS
The transect records are not reproduced here, as their content has
been embodied in diagrammatic form. A list of the total number of
each species recorded is given in the following table:—
Species No. recorded
Quercus petraea 181
Q. hybrids 91
Q, robur 38
Betula alba. 89
Carpinus betulus 47