132 F. E. Fritsch and E. J. Salisbury. 
flaccidum A. Br., which hence plays the role of a secondary 
coloniser. 
The only other cryptogams which play an important part on 
the land-slides are the lichen Bceomyces rufns DC. and Polytrichum 
piliferum, whilst the fungus Clavaria argillacea Pers. has a scattered 
distribution in the autumn. Both the alga Z. ericetorum and the 
lichen Bceomyces are encountered on burnt areas, but here they are 
almost confined to the sandy surface exposed by the creation of 
paths. 
Attention may be drawn to the fact that the cryptogamic flora, 
both in its constitution and in the succession of phases recalls the 
description given by Grsebner in his work on the North German 
heath (4, p. 82 et seq.). The species involved are in part the same. 
As has been pointed out by Warming (7, p. 208), Cladonias are 
often highly important peat-formers on heaths, and we have noticed 
that the lichen-flora does not reach any considerable development 
until four or five years after a fire. Estimations of the humus from 
burnt areas of various ages show no great difference in the amount 
during the first years subsequent to burning. It may well be, 
therefore, that Calluna remains puny, especially upon the slopes, 
until there is a sufficient accumulation of peat to admit of its 
vigorous development, and that this peat is largely produced by the 
abundant Cladonia -flora in later phases. As a matter of fact, 
measurements indicate that the average rate of growth of the 
Calluna , where the peat is deep, is more rapid than where the latter 
is shallow (poor Calluna). 
(2) Phanerogamic succession. 
Amongst early herbaceous colonisers seedlings of Carex 
pilulifera are universally frequent, sprouting stools as already stated 
being relatively rare. Other common colonisers are Polygala 
vulgaris, Rumex acetosella, Galium saxatile, Potentilla erecta, 
Epilobium angustifolium and Cuscuta epithytnum ,* those with wind- 
born seeds or fruits naturally appearing first. It is to be noted 
that Rumex acetosella, which on other heaths is often locally 
dominant after burning, is here never abundant over extensive 
areas, whilst Holcus lanatus is almost absent as a coloniser. The 
only grasses, of which seedlings are found in any quantity, are 
Air a flexuosa, Festuca ovina, Poa annua and Agrostis vulgaris. 
1 Apart from the hosts already mentioned (3, p. 159) this parasite has been 
found on Pteris, Aira, Triodia, Molinia, Agrostis, Erica tetralix, Potentilla erecta, 
Galium saxatile and sprouting Betula. 
