REPORT ON THE LICHENS OF EPPING FOREST. 99
lent eruptions on the upper surface of the thallus of the lichen :
when the ripe spores of the parasite are dispersed, each eruption
leaves a white spot in the lichen-thallus. This spot represents
the medullary layer, exposed by the decay of the algal com-
ponents of the cortical and gonidial layers, which, it is to be
presumed, the parasitic fungus chiefly attacks.
Coming now to our List of Additional Lichens recorded from
the Epping Forest district since the reading of our first paper
on 5th March, 1909. we have to call attention to the publication,
in the interim, of Miss A. Lorrain Smith's completion of the
British Museum Monograph on the Class2 ; this important
work considerably affects the nomenclature of these plants.
The systematic arrangement adopted by Miss Smith has been
uniformly followed in the following list, and. in addition, we
append a supplementary list of those forms included in our
first paper, the names of which have been altered in the work
mentioned.
The number of forms included in the present list is 63, which,
added to the 46 given in our former list, makes a total of 109.
fully-determined forms. We have again to express our grateful
thanks to Miss A. Lorrain Smith and to Mr. E. M. Holmes for
help in identifying critical forms.
Family—COLLEMACEI.
Tribe—COLLEMEI.
Collema furvum, Ach.
Several sterile examples, on a flat-topped tombstone in
St. Nicholas Churchyard, Loughton.
Family—LICHENACEI.
Tribe—CALICIEI.
Calicium melanophaeum, Ach., var. b. ferrugineum. Schaer.
On oak trunk, Green Ride near Loughton Camp ; fertile.
C. quercinum, Pers. Tent, f. chlorodes, Nyl.
On oak trunk between Woodberrie Hill and Green Ride ;
fertile.
C. trachelinum, Ach.
On oak trunk near Debden Slade ; fertile.
2 A Monograph of the British Lichens, Part II., by Annie Lorrain Smith, F.L.S., 1911.