K.- -BOTANY. 213 



if we plot on a map of the Arctic regions the distribution of ancient floras, 

 it becomes clear that no shifting of the earth's axis, even if this favourite 

 device were admissible, would give a satisfactory explanation of the con- 

 trast between the past and the present. These facts are well known ; 

 but it is time we made a more serious effort to solve the problems which 

 they raise. Discarding as inadequate, and as a method wholly displeasing 

 to astronomers, an attempt to create geographical environment consistent 

 with palseobotanical facts by altering the position of the North Pole, we 

 turn to the alternative of rearranging, within the Arctic Circle, the dis- 

 tribution of land and sea and the consequential shifting of cold and warm 

 oceanic streams. Assuming the permission of geologists to treat the earth's 

 crust as a jig-saw puzzle, we appeal to meterologists. Mr. Brooks in his 

 book on ' The Evolution of Climate ' suggests a possible rearrangement of 

 land and water which, he believes, would go some way towards the 

 provision of climatic conditions such as the fossil plants of the Tertiary 

 period appear to demand ; but it would seem from a more recent contribu- 

 tion by Dr. Simpson, the Head of the British Meteorological Department, 

 that we cannot hope to obtain all we need, or nearly all we need, by any 

 method of redistribution of land and sea on the assumption of a fixed pole 

 and without recourse to Wegener's hypothesis of drifting land areas. We 

 are left with two other alternatives : the adoption of Wegener's views or 

 some modification of them ; or the possibility that plants are less trust- 

 worthy as indices of climates than has generally been supposed. It may 

 be that a combination of these two methods of attack is the clue to our 

 problem. Let us take the second first : assuming that the ferns to which 

 reference has been made flourished on the parallels of latitude where their 

 remains have been found, and assuming such amelioration of the present 

 arctic conditions by a rearrangement of land and water as meteorologists 

 permit, there must have been in the past, as there is to-day, a long and 

 relatively dark period of sleep, and a summer no longer than the growing 

 season now available for the almost miraculous development of Arctic 

 plants. Can we imagine, to take one instance, the Cretaceous Flora of 

 Greenland enduring a sunless arctic night more than six months in 

 duration ? This raises a question to which no complete answer can be 

 given : we lack experimental data. It would be worth while to take 

 advantage of modern methods of research and devise means of reproducing 

 on a small scale the arctic summer season with continuous illumination 

 followed by a longer period of darkness. In considering possibilities we 

 must not forget the marked difference in the present position of the tree- 

 limit : in some places it dips far below the Arctic Circle, while in others it 

 invades much higher latitudes. In Western Greenland on latitude 70°N. 

 the willows seldom reach a height of three feet ; on the same latitude in 

 Canada and Alaska the White Spruce {Picea canadensis) attains fifty feet 

 in sheltered places. 



There is another, and to my mind an important and neglected considera- 

 tion ; we are too prone to speak of such a genus as Gleichenia as tropical 

 because it happens to be one of the commoner ferns in tropical countries ; 

 but, like many other genera characteristic of the warmer parts of the 

 world.it includes species which grow vigorously at an altitude of 10-12,000ft. 

 where the climate is by no means tropical. Is it not legitimate to 



