REGENERATION. 163 



An actual retrogressive development, a regressive succession, would neces- 

 sarily move backward through the same communities, represented by the same 

 phyads and reactions, as those through which the sere progressed. No one 

 has yet furnished the slightest evidence of such a development, and according 

 to the views set forth here, such a movement is absolutely impossible. It can 

 no more take place than an adult plant can be devolved again into a seedling 

 or a seed. The adult plant may be destroyed, and the seedling may take its 

 place. In like manner, a climax or subclimax community may be destroyed, 

 and an earlier associes develop in its stead. But a backward development is 

 as impossible in the one case as in the other. Destruction and reproduction 

 are the only possible processes. Even if one were to attempt to remove all 

 the individuals of each community in the reverse order of sequence, a true 

 retrogression comparable with the normal progression would still be impossible, 

 without at the same time destroying the reactions pari passu and estabUshing 

 the dominants of the next earlier associes. 



That the development after lumbering is the normal progression due to 

 partial denudation is shown by the observations of Adamovi6 (1899:144) in 

 the Balkans. He summarizes the secondary succession as follows: The first 

 stage occurs a few months after cutting. It is characterized by the disappear- 

 ance of shade plants, Oxalis, Actaea, Daphne, Deniaria, etc., and the increase 

 of the species found at the margin of the wood, such as Gerdiana, Salvia, 

 Knautia, Digitalis, Senedo, etc. The second stage is marked after a few years 

 by the development of a scrub of Corylus, Crataegus, Lonicera, etc., with an 

 undergrowth of Poa nemoralis, Rhinanthus, Pyrethrum, etc. The third stage 

 appears after 8 to 10 years, and is characterized by a young growth of Fagus, 

 Betula, Acer, and Sorbus, with a height of 5 to 6 feet. 



Degeneration. — It follows from the above that communities do not degen- 

 erate. They can only be destroyed with greater or less rapidity over larger 

 or smaller areas. As indicated above, there can be no thought of degeneration 

 when a forest is completely removed by fire, flood, or ax. This is too obviously 

 the normal process of denudation and secondary development. But when the 

 destruction is piecemeal, or when it acts through many years, the superficial 

 appearance of the community with its areas of normal structure side by side 

 with bits of earlier stages and actual bare spots seems to warrant the conclusion 

 that the community is degenerating. Such condition is strikingly shown in 

 the moors of the Pennines. The independent study of each area shows, how- 

 ever, that this is only a complex of moor communities in varying stages of 

 progressive development, alternating with areas exhibiting denudation in 

 different degrees. All so-called degenerating associations are to be explained 

 in the same way (plate 45 a). 



Regeneration. — ^WhUe the term "degeneration" is both incorrect and mis- 

 leading, no such objection can be brought against "regeneration" or "rejuvena- 

 tion." This follows quite naturally from the fact that succession is always 

 progressive, but never retrogressive. ^ A climax formation reproduces itself in 

 whole or in part, depending upon the degree of denudation. When the lat- 

 ter results in the production of a secondary area, the reproduction is essen- 

 tially that which occurs in the case of a plant regenerated from a leaf, and the 

 term "regeneration" might be appUed to all secondary succession. Rejuve- 

 nation is essentially synonymous, though it would seem to include primary 



