e evidence to support it； and it immediately raises the difficulty how did such a continent come to be stocked？
We must； however； agree with Hooker that the common origin of the northern and southern floras must be referred to a remote past。 That Darwin had this in his mind at the time of the publication of the 〃Origin〃 is clear from a letter to Hooker。 〃The view which I should have looked at as perhaps most probable （though it hardly differs from yours） is that the whole world during the Secondary ages was inhabited by marsupials； araucarias （Mem。Fossil wood of this nature in South America）； Banksia； etc。； and that these were supplanted and exterminated in the greater area of the north； but were left alive in the south。〃 （Ibid。 I。 page 453。） Remembering that Araucaria； unlike Banksia； belongs to the earlier Jurassic not to the angiospermous flora； this view is a germinal idea of the widest generality。
The extraordinary congestion in species of the peninsulas of the Old World points to the long…continued action of a migration southwards。 Each is in fact a cul…de…sac into which they have poured and from which there is no escape。 On the other hand the high degree of specialisation in the southern floras and the little power the species possess of holding their own in competition or in adaptation to new conditions point to long… continued isolation。 〃An island。。。will prevent free immigration and competition； hence a greater number of ancient forms will survive。〃 （Ibid。 I。 page 481。） But variability is itself subject to variation。 The nemesis of a high degree of protected specialisation is the loss of adaptability。 （See Lyell； 〃The Geological Evidences of the Antiquity of Man〃； London； 1863； page 446。） It is probable that many elements of the southern flora are doomed： there is； for example； reason to think that the singular Stapelieae of S。 Africa are a disappearing group。 The tree Lobelias which linger in the mountains of Central Africa； in Tropical America and in the Sandwich Islands have the aspect of extreme antiquity。 I may add a further striking illustration from Professor Seward： 〃The tall； graceful fronds of Matonia pectinata； forming miniature forests on the slopes of Mount Ophir and other districts in the Malay Peninsula in association with Dipteris conjugata and Dipteris lobbiana； represent a phase of Mesozoic life which survives
'Like a dim picture of the drowned past。'〃 （〃Report of the 73rd Meeting of the British Assoc。〃 （Southport； 1903）； London； 1904； page 844。）
The Matonineae are ferns with an unusually complex vascular system and were abundant 〃in the northern hemisphere during the earlier part of the Mesozoic era。〃
It was fortunate for science that Wallace took up the task which his colleague had abandoned。 Writing to him on the publication of his 〃Geographical Distribution of Animals〃 Darwin said： 〃I feel sure that you have laid a broad and safe foundation for all future work on Distribution。 How interesting it will be to see hereafter plants treated in strict relation to your views。〃 （〃More Letters〃； II。 page 12。） This hope was fulfilled in 〃Island Life〃。 I may quote a passage from it which admirably summarises the contrast between the northern and the southern floras。
〃Instead of the enormous northern area； in which highly organised and dominant groups of plants have been developed gifted with great colonising and aggressive powers； we have in the south three comparatively small and detached areas； in which rich floras have been developed with SPECIAL adaptations to soil； climate； and organic environment； but comparatively impotent and inferior beyond their own domain。〃 （Wallace； 〃Island Life〃； pages 527； 528。）
It will be noticed that in the summary I have attempted to give of the history of the subject； efforts have been concentrated on bringing into relation the temperate floras of the northern and southern hemispheres； but no account has been taken of the rich tropical vegetation which belts the world and little to account for the original starting…point of existing vegetation generally。 It must be remembered on the one hand that our detailed knowledge of the floras of the tropics is still very incomplete and far inferior to that of temperate regions； on the other hand palaeontological discoveries have put the problem in an entirely new light。 Well might Darwin； writing to Heer in 1875； say： 〃Many as have been the wonderful discoveries in Geology during the last half…century； I think none have exceeded in interest your results with respect to the plants which formerly existed in the arctic regions。〃 （〃More Letters〃； II。 page 240。）
As early as 1848 Debey had described from the Upper Cretaceous rocks of Aix…la…Chapelle Flowering plants of as high a degree of development as those now existing。 The fact was commented upon by Hooker （〃Introd。 Essay to the Flora of Tasmania〃； page xx。）； but its full significance seems to have been scarcely appreciated。 For it implied not merely that their evolution must have taken place but the foundations of existing distribution must have been laid in a preceding age。 We now know from the discoveries of the last fifty years that the remains of the Neocomian flora occur over an area extending through 30 deg of latitude。 The conclusion is irresistible that within this was its centre of distribution and probably of origin。
Darwin was immensely impressed with the outburst on the world of a fully fledged angiospermous vegetation。 He warmly approved the brilliant theory of Saporta that this happened 〃as soon （as） flower…frequenting insects were developed and favoured intercrossing。〃 （〃More Letters〃； II。 page 21。） Writing to him in 1877 he says： 〃Your idea that dicotyledonous plants were not developed in force until sucking insects had been evolved seems to me a splendid one。 I am surprised that the idea never occurred to me； but this is always the case when one first hears a new and simple explanation of some mysterious phenomenon。〃 （〃Life and Letters〃； III。 page 285。 Substantially the same idea had occurred earlier to F。W。A。 Miquel。 Remarking that 〃sucking insects （Haustellata）。。。perform in nature the important duty of maintaining the existence of the vegetable kingdom； at least as far as the higher orders are concerned；〃 he points our that 〃the appearance in great numbers of haustellate insects occurs at and after the Cretaceous epoch； when the plants with pollen and closed carpels （Angiosperms） are found； and acquire little by little the preponderance in the vegetable kingdom。〃 〃Archives Neerlandaises〃； III。 （1868）。 English translation in 〃Journ。 of Bot。〃 1869； page 101。）
Even with this help the abruptness still remains an almost insoluble problem； though a forecast of floral structure is now recognised in some Jurassic and Lower Cretaceous plants。 But the gap between this and the structural complexity and diversity of angiosperms is enormous。 Darwin thought that the evolution might have been accomplished during a period of prolonged isolation。 Writing to Hooker （1881） he says： 〃Nothing is more extraordinary in the history of the Vegetable Kingdom； as it seems to me； than the APPARENTLY very sudden or abrupt development of the higher plants。 I have sometimes speculated whether there did not exist somewhere during long ages an extremely isolated continent； perhaps near the South Pole。〃 （〃Life and Letters〃； III。 page 248。）
The present trend of evidence is； however； all in favour of a northern origin for flowering plants； and we can only appeal to the imperfection of the geological record as a last resource to extricate us from the difficulty of tracing the process。 But Darwin's instinct that at some time or other the southern hemisphere had played an important part in the evolution of the vegetable kingdom did not mislead him。 Nothing probably would have given him greater satisfaction than the masterly summary in which Seward has brought together the evidence for the origin of the Glossopteris flora in Gondwana land。
〃A vast continental area； of which remnants are preserved in Australia； South Africa and South America。。。A tract of enormous extent occupying 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 la