The variation in height and density of the fronds in the hinterland of area D is confirmed as stages in the development of bracken from the pioneer to the mature phase. Factors affecting its rate are winter and spring frost and rainfall. In the absence of interference there would appear to be no degenerate phase such as has been described as part of a natural cycle of change in the hinterland of area E.
By the use of thatch and cage development is expedited but later reactions ensue affecting the number of fronds, their height, spindliness and depth of origin such as are found in the degenerate phase in area E. Thatch and cage induce degeneration in area D and probably accentuate it in area E.
The mechanism of degeneration requires detailed investigation but it would appear to involve the change from a community (mature phase) in area D where the old shoots are dispersed singly or at most in small groups in an uneven-aged population to one in which they are aggregated in larger more or less even-aged patches such as are found in area E.
In the contrast between the hinterlands of area D and area E as well as in phasic development, litter, its amount and kind, emerges as important. Burning removes this litter and its influence on bracken in different phases, leading in some to retrogression and even local extinction, in others to rejuvenation, is discussed.