TRANSACTIONS OF SECTION K. 579 



Communications were then read from Professor P. F. Kendall and Dr. J. 

 E. Marr, F.R.S. 



Professor Kendall said in his letter that Mr. Reid had extended to the 

 whole of the British Isles a generalisation he himself had ventured to apply 

 nearly twenty years ago to the case of the Isle of Man. For the purposes of 

 this discussion he would restate some of the salient facts regarding the latter 

 island. It possesses a varied relief with hills ranging up to 2,034 feet. The sur- 

 face presents a variety of conditions, from swamp and heath to rocky hills and 

 narrow glens; while the geological constituents afforded a wide diversity of 

 soil and subsoil. The hydrographic features are correspondingly varied, and 

 the climate is remarkably equable. An island thus constituted would offer con- 

 ditions favourable to the maintenance of a large flora and fauna — yet the island 

 is remarkably poor in the number of species of plants, and the indigenous fresh- 

 water fishes, amphibia, reptiles, and mammals do not together number a dozen 

 species. 



The explanation seems clear that since the departure of the great ice-sheet, 

 beneath which the island was completely overwhelmed, there has been no land- 

 bridge across which terrestrial plants and vertebrates could travel. The whole 

 fauna and flora has been introduced by chance agencies across the Irish Sea. 

 He was of opinion that since the departure of the ice, no part of the British 

 Isles had been connected with the continent. 



Dr. J. E. Marr pointed out that it is generally admitted that after the 

 Great Ice Age a period occurred which was marked by widespread steppe con- 

 ditions in Europe and elsewhere. We should expect survivals of this period to 

 exist in areas not now under steppe conditions, just as survivals of the earlier 

 Glacial Period do so where ice and snow no longer occupy the hills all the year 

 round. 



A group of xerophytes is found growing on the heaths of the Brecklands of 

 North Suffolk and South Norfolk, many of which are not known elsewhere in 

 Britain. It is true that they are also found on the physically similar heaths of 

 North Germany, but in both cases they may be survivals from the steppe 

 period, which have lingered on in spots where the local conditions somewhat 

 resemble those of steppes. 



Professor 0. Drtjde maintained that the problem could only be satisfactorily 

 attacked by considering continental evidence (e.g., from the Alps, Germany, 

 Scandinavia, &c), as well as that furnished by Great Britain itself. In Ger- 

 many, for example, during the comparatively late 'Baltic Ice Age,' when North- 

 West Germany was already free from ice, there existed in Saxony a curious 

 mingling of species of various types, e.g., forests of Picca excel sa, boreal forms 

 such as Ledum Linnan, &c, and also Atlantic species, such as Hymeno- 

 phyttum tunbndgense. Why are these boreal species absent from the moist 

 climate of South England, where they could well grow on the heaths ? Prof. 

 Drude answered this question by suggesting that South England was occupied, 

 even' during glacial times, by Atlantic and Lusitanian species. Although he 

 thought many species survived, some may have been introduced in post-glacial 

 times. 



Dr. F. J. Lewis said that in his opinion the existence of submerged peat 

 and also of buried forests in places where tree life is now impossible (e.g., the 

 western coasts of the Outer Hebrides) point to a former much greater extent of 

 land surface. He thought Mr. Reid had underestimated the relative changes in 

 level of sea and land. With regard to the parallel drawn between Krakatoa 

 and the British Isles, the conditions were so different, that no reliable compari- 

 son could be made between re-immigration across a tropical sea, and the same 

 process across a strait in cool temperate latitudes. 



Dr. C. H. Ostenfeld agreed with Mr. Reid that no temperate species sur- 

 vived the Glacial Period in Britain. The importance of ' Nunataks ' (on which 

 plants may have survived) is probably overestimated : it is very difficult to pro- 

 duce conclusive evidence as to whether a mountain summit has, or has not, been 

 glaciated. He was of opinion that the present flora of Britain originated some- 

 what as follows : (1) The arctic-alpine species survived the glacial period, 

 mainly in the South of England ; (2) the bulk of the flora crossed from the con- 

 tinent by means of a land connection; and (3) some few species (with small 



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