282 PAULSON : NOTES ON THE ECOLOGY OF LICHENS.
Thompson5. During the autumn of 1917, there was a remarkable
growth of Lecidea uliginosa Ach. on heaths and commons around
London, upon soil that had been worn bare during the previous
summer through various causes. It appeared as a dark, almost
black, stain upon the ground. Patches as long as 8ft. by 6ft.
were measured at the Cryptogamic meeting of the Essex Field
Club, on 10th November last, on the open ground in front of
the King's Oak Hotel, High Beach. The abundance of fertile
Baeomyces roseus Pers, near Oak Hill was seen at the same
meeting. It has not been fertile there for at least twelve years.
When considering the rate of growth of lichens, it is very
necessary to distinguish between those with a thallus of very
loosely-woven threads and those with a well-developed foliose
thallus. The two just described have the former texture. Hav-
ing asked a correspondent, a well known lichenist of Yorkshire,
5 Essex Naturalist, vol. xviii., p. 29 (1915).