370 ANNUAL REPORT SMITHSONIAN INSTITUTION, 193 2 



Island, approximately 1,200 miles from the North Pole, there are 

 beds of sand and clay with bands of lignite which were deposited as 

 sediment in a bay of the Cretaceous sea and subsequently upraised. 

 In these rocks have been found many fossil plants which bear no 

 resemblance and show only distant relationship to the components 

 of the present flora. The commonest Cretaceous ferns are closely 

 allied to species of the genus Gleichenia that is now widely spread 

 in the southern Tropics and entirely unknown in Europe and in 

 almost the whole of North America, 



Trees were represented by several kinds of Plat anus (the syca- 

 more of North America; the planetree of England), a genus now 

 living in eastern North America, in a narrower territory along the 

 more southern part of the Pacific coast, in Greece and Asia Minor: 

 by several different conifers, including one related to the redwoods 

 of California and Oregon, another allied to the umbrella-pine of 

 Japan. There were also magnolias, an Artocavpus closely resembling 

 in leaf and inflorescence the tropical breadfruit tree, and trees bear- 

 ing leaves hardly distinguishable from those of the maidenhair-tree 

 {Ginkgo hiloha) which, it is said, no longer occurs in a wild state. 

 The Cretaceous flora of Greenland is made up of many different 

 plants, several of them belonging to genera that are now represented 

 by tropical, subtropical, or temperate species. Others are extinct 

 genera. It would seem that we might reasonably conclude from the 

 evidence of the fossils that Cretaceous Greenland enjoyed a sub- 

 tropical climate. There are, however, serious objections to this in- 

 ference : we are hardly at liberty to assume that extinct species — and 

 all the Greenland plants are extinct species — lived under climatic 

 conditions identical with or even very near to those required by their 

 modern descendants. It is well known that some existing plants are 

 tolerant of a wide range of temperature and other phj^sical condi- 

 tions, also that closely allied plants often live under very different 

 conditions. Moreover, it is conceivable that in the course of ages 

 genera and families of plants may have undergone a change in their 

 constitution; plants that are now unable to endure an Arctic or a 

 temperate climate may formerly have been less sensitive and hardier. 

 May we not think of change in the adaptability of an organism as 

 well as of change in structure acquired in the course of thousands, 

 or it may be, millions of years? 



It is possible by altering the distribution of land and water to 

 change the direction of currents in the sea and air and thus modify 

 the factors governing climate; but it is doubtful whether any such 

 alteration could so far amelioriate the climate of an Arctic land as 

 to fulfill the conditions which seem to be indicated by the Cretaceous 

 flora. There are two possibilities : First, the assumption, and it is 



