Ancestry of Angios2)erms 315 



it at the present time. It is not unreasonable to suppose that both 

 phenomena, so similar, may admit of the same explanation. I confess 

 it would not surprise me if fresh discoveries in the distribution of 

 the Glossopteris flora were to point to the possibility of its also 

 having migrated southwards from a centre of origin in the northern 

 hemisphere. 



Darwin, however, remained sceptical "about the travelling of 

 plants from the north except during the Tertiary periody But 

 he added, "such speculations seem to me hardly scientific, seeing 

 how little we know of the old floras \" That in later geological 

 times the south has been the grave of the weakened offspring of 

 the aggressive north can hardly be doubted. But if we look to 

 the Glossopteris flora for the ancestry of Angiosperms during the 

 Secondary period, Darwin's prevision might be justified, though he 

 has given us no clue as to how he arrived at it. 



It may be true that technically Darwin was not a botanist. But 

 in two pages of the Origin he has given us a masterly explanation 

 of "the relationship, with very little identity, between the productions 

 of North America and Europe-." He showed that this could be 

 accounted for by their migration southwards from a common area, 

 and he told Wallace that he " doubted much whether the now called 

 Palaearctic and Nearctic regions ought to be separated^." Catkin- 

 bearing deciduous trees had long been seen to justify Darwin's doubt : 

 oaks, chestnuts, beeches, hazels, hornbeams, birches, alders, willows 

 and poplars are common both to the Old and New World. Newton 

 found that the separate regions could not be sustained for birds, and 

 he is now usually followed in uniting them as the Holarctic. One feels 

 inclined to say in reading the two pages, as Lord Kelvin did to a 

 correspondent who asked for some further development of one of 

 his papers. It is all there. We have only to apply the principle 

 to previous geological ages to understand why the flora of the 

 Southern United States preserves a Cretaceous facies. Applying it 

 still further we can understand why, when the northern hemisphere 

 gradually cooled through the Tertiary period, the plants of the 

 Eocene "suggest a comparison of the climate and forests with those 

 of the Malay Archipelago and Tropical America*." Writing to 

 Asa Gray in 185G with respect to the United States flora, Darwin 

 said that " Nothing has surprised me more than the greater generic 

 and specific affinity with East Asia than with West America ^" The 

 recent discoveries of a Tulip tree and a Sassafras in China afford 



» Life and Letten, in, p. 247. * pp. 333, 334. 



* Life and Letters, in. p. 230. 



* Clement Reid, Encycl. Drit. (10th edit.), Vol. xsxi. ("Palaeobotany; Tertiary"), 

 p. 435. 



* More Letten, i. p. 434. 



