Darwin and Modern Science [218]
an area, part of which has since given place to a southern ocean, while detached masses persist as portions of more modern continents, which have enabled us to read in their fossil plants and ice-scratched boulders the records of a lost continent, in which the Mesozoic vegetation of the northern continent had its birth." ("Encycl. Brit." (10th edition 1902), Vol. XXXI. ("Palaeobotany; Mesozoic"), page 422.) Darwin would probably have demurred on physical grounds to the extent of the continent, and preferred to account for the transoceanic distribution of its flora by the same means which must have accomplished it on land.
It must in fairness be added that Guppy's later views give some support to the conjectural existence of the "lost continent." "The distribution of the genus Dammara" (Agathis) led him to modify his earlier conclusions. He tells us:--"In my volume on the geology of Vanua Levu it was shown that the Tertiary period was an age of submergence in the Western Pacific, and a disbelief in any previous continental condition was expressed. My later view is more in accordance with that of Wichmann, who, on geological grounds, contended that the islands of the Western Pacific were in a continental condition during the Palaeozoic and Mesozoic periods, and that their submergence and subsequent emergence took place in Tertiary times." (Guppy, op. cit. II. page 304.)
The weight of the geological evidence I am unable to scrutinise. But though I must admit the possibility of some unconscious bias in my own mind on the subject, I am impressed with the fact that the known distribution of the Glossopteris flora in the southern hemisphere is precisely paralleled by that of Proteaceae and Restiaceae in 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 PERIOD." But he added, "such speculations seem to me hardly scientific, seeing how little we know of the old floras." ("Life and Letters", III. page 247.) 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." (Pages 333, 334.) 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 Neartic regions ought to be separated." ("Life and Letters", III. page 230.) 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 Holartic. 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
It must in fairness be added that Guppy's later views give some support to the conjectural existence of the "lost continent." "The distribution of the genus Dammara" (Agathis) led him to modify his earlier conclusions. He tells us:--"In my volume on the geology of Vanua Levu it was shown that the Tertiary period was an age of submergence in the Western Pacific, and a disbelief in any previous continental condition was expressed. My later view is more in accordance with that of Wichmann, who, on geological grounds, contended that the islands of the Western Pacific were in a continental condition during the Palaeozoic and Mesozoic periods, and that their submergence and subsequent emergence took place in Tertiary times." (Guppy, op. cit. II. page 304.)
The weight of the geological evidence I am unable to scrutinise. But though I must admit the possibility of some unconscious bias in my own mind on the subject, I am impressed with the fact that the known distribution of the Glossopteris flora in the southern hemisphere is precisely paralleled by that of Proteaceae and Restiaceae in 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 PERIOD." But he added, "such speculations seem to me hardly scientific, seeing how little we know of the old floras." ("Life and Letters", III. page 247.) 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." (Pages 333, 334.) 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 Neartic regions ought to be separated." ("Life and Letters", III. page 230.) 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 Holartic. 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