156 DIRECTION OF DEVELOPMENT. 



of intensive quantitative studies for a period of years so few that there is 

 hardly a case in which conclusive proof is available. The well-nigh universal 

 opinion of European workers in this matter merely constitutes an excellent 

 working hypothesis, which can be accepted only after the most rigorous tests 

 by exact ecology. The Uterature upon this subject is vast, but while much of 

 it is suggestive, little is convincii^. The dearth of conclusive evidence may 

 best be indicated by the following statements from recent investigations. 

 Graebner (1901:97) says: 



"In spite of the numerous moors with roots and upright stems that I have 

 seen, for a long time I was unable to discover the swamping of a forest in the 

 actual beginning of development. Finally, however, I had the opportunity 

 of seeing two such moors in process of formation. One of these was found near 

 Salm in western Prussia, the other at Kolbermoor in upper Bavaria." 



Status of forest in Britain.— The difficulties of determining the actual changes 

 of woodland in the past may be gained from the statement of Moss, Rankin, 

 and Tansley (1910:114): 



"In a country like England, much of which has been cultivated and thickly 

 populated for centuries, it may be asked, do there remain any natural wood- 

 lands at all? Have not existing woods been so altered by planting and in 

 other ways that they no longer represent the native plant communities, but 

 are rather to be considered as mere congeries of indigenous and introduced 

 species? 



"It is undoubtedly true that there is little 'Urwald' or true virgin forest 

 reraaining in the country, though some of the woods, especially near the upper 

 limit of woodland in the more mountainous regions, might make good their 

 claim to this title. On the other hand, there are, of course, many plantations 

 pure and simple which have been made on moorland, heath, grassland, or 

 arable land, and which may of course consist of native or of exotic trees or of 

 a mixture of the two. But between these two extremes, according to the con- 

 clusions of all the members of the British Vegetation Committee who have 

 given any special attention to this subject, come the great majority of the British 

 woods; which are neither virgin forest, nor plantations de novo, but are the 

 lineal descendants, so to speak, of primitive woods. Such semi-natural woods, 

 though often more or less planted, retain the essential features of natural woods 

 as opposed to plantations, and without any reasonable doubt are characterized 

 by many of the species which inhabited them in their original or virgin con- 

 dition." 



Moss (1913 : 111) concludes that: 



"Whilst opinions may differ as to whether or not the grassland just described 

 is wholly or only in part due to man's interference, it appears to be generally 

 accepted that such tracts were formerly clothed with forest; and Warming 

 (1909:326) even goes so far as to say that 'were the human race to die out,' 

 the grassla,nds of the lowlands of northern Europe 'would once more be seized 

 by forest, just as their soil was originally stolen from forest.' As regards the 

 Nardus grassland of the hill slopes of this district, it seems incontestable that 

 it is an association which has, on the whole, resulted from the degeneration of 

 oak and birch woods. The fundamental conditions of the habitat have been 

 but slightly altered in the process; and, therefore, the oak and birch woods, 

 the Nardus grassland, and the various transitional stages of scrub are placed 

 in one and the same plant formation." 



