Further Observations on Heath Association. 135 
Of the shrubby members, seedlings are commonly found only 
in the case of Ulex nanus , Calluna, and Erica cinerea. Large 
numbers of seedlings of the first-named appear almost immediately 
after a fire, but the vast majority of these subsequently die. Thus, 
on F 1 (burnt June, 1913) numerous healthy U. nanus seedlings 
were found in the April succeeding the fire ; two months later (in 
June) from five to ten per cent, of these were dead, whilst in 
October the number of dead seedlings was still larger. The 
abundant U. nanus seedlings previously recorded on F 3 (3, pp. 
156,157) in January, 1912, were represented by only a few survivals 
in June, 1914. The Erica cincrea and Calluna seedlings which 
appear slightly later are very numerous, as shown in Table IX, and 
a large percentage of these are destined to survive. It is to be 
noted that the burnt stools of these two forms rarely rejuvenate 
(p. 119), and therefore their presence in the mature heath depends 
largely on the survival of seedlings. Moreover, since the U. nanus 
mostly rejuvenates, it not only obtains a start over the later- 
appearing Ericas and Callunas, but the shoots, growing as they do, 
from an already established root-system, will at first develop much 
more vigorously than the seedlings of the other two genera. 
TABLE IX. 
Number of Seedlings per Twenty-Five Square Feet of 
Burnt Area (April, 1914). 
Locality. Ulex nanus. Calluna. Erica cinerea. Vaccinium. 
F 2 ... 430 ... 574 ... 19,068 ... 6 
P 3 ... 87 ... 4,641 ... 11,513 ... — 
Seedlings of Erica tetralix are rarely found on newly burnt 
areas except where these adjoin the damper depressions in which 
this species occurs in some quantity. Vaccittum seedlings are also 
sparse (see Table IX), possibly in part owing to the paucity of the 
peat, in part to the fruits being largely dispersed by birds which do 
not settle frequently on the burnt areas. 
The extent to which seeds of the typical heath representatives, 
already present in the peat, play a part in colonisation is uncertain 
(cf. 5, p. 179), but it may be mentioned that such seeds do occur, 
though only those of Erica cinerea have been found in any quantity. 
It is quite probable that the hard caked crust, formed by the charred 
peat, may retard colonisation by seeds falling on the surface. An 
experiment with cress seeds showed that these germinate quite 
readily on the broken charred surface, but of an equal number sown 
