286 THE ESSEX NATURALIST.
Wheldon, J. A. and Wilson, A. :—No. (6), Sect. I., 1915.
17. Farrow, E. Pickworth :—On the Ecology of the Vegetation of
Breckland. Journ. of Ecology, vol. vi., No. 2, pp. 144-152,
1918.
18. Paulson, R. :—Notes on the Ecology of Lichens, with special
reference to Epping Forest. Essex Naturalist, vol. xviii.,
1918.
Watson, W, :—No. (9) b, c. and d., Sect. I., 1918 and 1919.
Section III. Morphology and Physiology.
19. Darbishire, O. V. :—The Development of the Apothecium in the
Lichen Peltigera, Brit. Ass. Adv. Sci. (abstract), 1913.
20. Paulson, R. and Hastings, Somerville :—A Wandering Lichen.
Knowledge, vol. xxxviii., 1914.
31. Porter, Lilian :—Attachment Organs of Corticolous Ramalineae.
Proc. Roy. Irish Acad., vol. xxxiv., 1919.
Section IV. Symbiosis.
22. Smith, A. Lorrain :—Relation of Fungi to other Organisms. Trans.
Brit. Mycol. Soc, pp. 26-29, 1917.
23. Paulson, R. and Hastings, Somerville :—Relation between the
Alga and Fungus of a Lichen. Journ. Linn. Soc. (Bot.),
vol. xliv., 1920.
24. Church, A. H. :—The Lichen Symbiosis, Journ. Bot., vol. lviii., 1920.
25. Church, A. H. :—The Lichen as Transmigrant. Journ. Bot., vol.
lix., 1921.
26. Paulson, R. :—The Sporulation of Gonidia in the Thallus of Evernia
prunastri, Trans. Brit. Mycol. Soc, vol. vii., 1921.
Notes on Lichens included in papers on Allied Subjects, etc.
27. Cotton, A. D. :—Marine Algae, Clare Island Survey, part 15. Proc
Roy. Irish Acad., vol. xxxi., 1912, pp. 19-20 and 26-28.
28. Wheldon, J. A. :—A Westmoreland Lichen. Lancashire Nat.,
vol. lviii., 1916.
29. Lyle, Lilian :—The Marine Algae of Guernsey. Journ. Bot., vol.
lviii., 1920, pp. 35-36 and 38-39.
Books.
30. Tansley, A. G. :—Types of British Vegetation, Cambridge, Univers-
ity Press, 1911, Chapt. xiii.
31. Smith, A. Lorrain :—A Monograph of British Lichens, part. II,
London 1911. Part I., 1918.
32. Smith, A. Lorrain :—A Handbook of the British Lichens, London,
1921.*
33. Smith, A. Lorrain :—Lichens, Cambridge Botanical Handbooks,
Cambridge University Press, 1921.*
DESCRIPTION OF THE PLATES.
Plate XXIII. Fig. 1. Trans. sect. of a squamule of the thallus of 
Cladonia digitata Hoffm. (a) upper cortical
layer ; (b) gonidial layer ; (c) medullary layer.
The gonidia occur in spherical groups. X 240.
*These have been published since the foregoing address was delivered.