168
THE ESSEX NATURALIST
in common. It is difficult to be absolutely precise in these comparisons
because of changes in taxonomy and in the circumscriptions of certain
species.
Lecanora varia was included in the list of 1924, but this almost
certainly referred to L. conizaeoides which is abundant in the forest,
as it generally is to-day in eastern and central England. There has been
much confusion in the past between these species, but it is now realised
that L. varia (Ehrh.) Ach. in the proper sense is not very common in
this country and that most of the older records refer to L. conizaeoides.
It is interesting that no name which could have referred to this species
was given in the list of 1890.
Lecanora subfusca var. allophana (Ach.) Rohl. was recorded in
1924, and simply 'L. subfusca' (probably in a broad sense) in 1890.
I encountered only L. chlarotera f. rugosella of this group.
Ochrolechia subviridis is a lichen which until recently has been com-
pletely overlooked in this country (see Laundon, 1958, The Lichenol-
ogist, I, p.37). It is probably of frequent occurrence on trees. It appears
that it is always sterile, but its coarsely powdery thallus, grey-green in
colour except for the smooth white margin, and its striking red reaction
with calcium hypochlorite render it quite distinctive. It is here recorded
for Essex for the first time. So also is Parmelia scortca, which was
found on a dead tree close to the south-eastern entrance to the forest.
The bright yellowish-green thallus of Lecidea lucida in its usual
sterile condition was seen on the bricks of the boathouse. No specimen
could therefore be collected for expert verification.
In 1890 only one species of Cladonia was listed; this was 'C pyxidata'
which probably referred to C. chlorophaea. However, the genus now
appears to be quite well represented. C. parasitica, consisting of a mass
of extremely small scales but with a few fertile podetia was found
several times on decaying stumps and logs. This is another species that
is probably much commoner than the existing records would indicate.
C. floerkeana which, somewhat surprisingly, has not previously been
recorded for N. Essex, is a common heathland species. It may be com-
paratively rare in the county because of a scarcity of suitable habitats.
It was found in small quantity on two decayed stumps in an exposed
situation.
Cladonia fimbriata (L.) Fr. in the strict sense was not encountered,
but C. coniocraea was abundant on the basal parts of tree-trunks and
decaying stumps, and C. cornutoradiata was found on one exposed
stump. Both of these species are sometimes classified under the name
'C. fimbriata' and the reference to this species in 1924 may well have
applied to one or both of these.
The two species C. furcata and C. rangiformis are morphologically
rather similar and apt to be confused. Their ecological requirements
are believed to be different. At Hatfield Forest they were not found
growing together; C. furcata was amongst grass and Polytrichum on a