June, 1913. 



KNOWLEDGE. 



213 



the Glacial epoch there. But if this flora survived, 

 in Glacial Greenland, the necessarily severe con- 

 ditions, may we not be almost absolutely certain that 

 our flora could survive in milder Glacial England ? 



And then there arises the interesting botanical 

 question : Does it require a plant to be of a hardier 

 constitution to stand being covered with snow or ice 

 for several months, and then have a warm summer 

 — as it would during glaciation — or to be alternately 

 frozen and thawed — as it is apt to be in our uncertain 

 climate to-day ? In other words, would it kill any 

 of our native species to be so treated? A deep cover- 

 ing of snow and ice, in fact, keeps the earth warm. 

 That is why we usually see a stream of water 

 issuing from beneath a glacier. And it is to be 

 remembered that a country covered with ice and 

 snow is not necessarily as cold as Siberia, or the 

 Antarctic. Nor because an ice-sheet or glacier came 

 down to the latitude of London need we suppose that 

 a temperate vegetation could not flourish there. At 

 present alpine glaciers end amid a varied flora, while 

 in New Zealand glaciers come down to the regions 

 of a sub-tropical vegetation. In North America, 

 again, the limits of the forest go up into the ice, and 

 the limits of the ice come down into the forests. Ice 

 and snow require only a temperature of 32° F. for 

 their formation, and unless there are other causes 

 than the presence of these, there need not be intense 

 cold. And it is to be remembered that every pound 

 of water frozen means the setting free of enough 

 heat to raise eighty pounds of water 1° C. Hence 

 the enormous quantities of ice and snow imagined 

 by extreme glacialists do not necessarily imply a 

 proportionately lower temperature. The cold is, so 

 to speak, used up in freezing the water. 



The fact that our little group of plants is confined 

 to the south-west corner of Ireland, and that they 

 are Spanish plants, inclines us to view them as 

 tender species. And this makes one of the special 

 difficulties of the case. How could such tender 

 species survive ? But may they not in reality be 

 hardier than the facts suggest ? The Arbutus 

 stands the winter and ripens its fruit in the southern 

 counties of England, while London Pride is a 

 perfectly hardy plant which does not suffer in our 

 severest winters. Information as to the altitudes 

 attained by the various species in the Pyrenees 

 might help to settle this point. And the fact that 

 some of our species are also natives of Greenland 

 suggests that a group of Spanish plants might be 

 hardy enough to be natives also of a more northern 

 latitude. 



But it may be asked, If our plants did survive 

 glaciation, ought there not to be some positive 

 evidence in the form of fossils ? The difficulty of 

 obtaining such actual evidence of survival in glacial 

 deposits arises from the fact that many geologists 

 believe that there have been several Glacial periods 

 in Pleistocene times. Thus, if remains of temperate 

 plants are found in such Glacial deposits, the actual 

 beds containing them are classed as inter-Glacial. 

 The plants which had been exterminated by the cold 

 are supposed to have come back during a warm 

 inter-Glacial period. Personally, we have defended 

 the case of one Pleistocene Glacial epoch (Geological 

 Magazine, August and September, 1891). And, if 

 this is correct, then there is abundant evidence of 

 the survival of temperate plants during glaciation. 

 But, even on the view of several glaciations, there 

 are not wanting cases where temperate species occur 

 in deposits which are classed as Glacial by reason of 

 the Arctic species which they also contain. Mr. 

 Clement Reid, who advocates the view of several 

 Glacial epochs, and believes that all temperate species 

 were exterminated by the cold, gives detailed lists of 

 species found in various Glacial, and so-called inter- 

 Glacial, deposits. Glancing through these as 

 given in his " Origin of the British Flora," we realise 

 that it must often have been extremely difficult to 

 the author to decide from the plant remains whether 

 the deposit should be classed as Glacial or inter- 

 Glacial. We will take one or two illustrations of 

 this from the above work in support of our con- 

 tention. Thus, a deposit near Edinburgh is described 

 as follows : — 



"In the lower part of the lacustrine deposits 

 filling a silted-up lake are numerous seeds and leaves 

 of Arctic plants. The deposit is probably Late 

 Glacial." 



Yet the plant list appended contains such 

 temperate forms as the Creeping Buttercup, the 

 Marsh Violet, the Dandelion, the Bogbean, and so on. 



Another deposit, yielding Arctic plants, has in 

 addition to the above temperate forms, Campion, 

 Wood Sorrel, Knot-grass, and so on. Examples of 

 such mingling of Arctic and temperate forms might 

 be multiplied, and even on Mr. Clement Reid's own 

 interpretation of the order of events they seem to 

 indicate the survival of the latter. 



Finally, if there is no evidence of a />osr-Glacial 

 land connection, and if we cannot satisfactorily 

 account for the presence of the peculiar flora of 

 south-west Ireland by other means of dispersal, 

 this in itself is a proof of the possibility of survival. 



ANNOUNCEMENTS. 



EUGENICS as a practical science is now recognised by 

 sociologists as an important factor in race culture ; and the 

 Eugenic Club Committee cordially invite the co-operation of 

 ladies and gentlemen who are interested in Eugenics and 

 kindred subjects to communicate with the Secretary, 6, Hand 

 Court, High Holborn, W.C. 



MUSEUM EXTENSION AT HULL.— A further valuable 



gift has just been made to the Hull Municipal Museums Com- 

 mittee by C. Pickering, Esq., J. P., the donor of the new Museum 

 of Fisheries and Shipping at the Pickering Park. It was 

 recently represented to him that the new museum was already 

 crowded with exhibits, and he has kindly presented a strip of 

 land stretching from the Hessle Road to the Pickering Park, and 

 adjoining the present museum, for the purpose of extension. 



