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nd capacities that have been developed in other connections。〃 （Loc。 cit。 page 102。） 〃Their utility in these respects is an accident in the plant's life。〃 （Loc。 cit。 page 100。） He attributes this utility to a 〃determining agency；〃 an influence which constantly reappears in various shapes in the literature of Evolution and is ultra…scientific in the sense that it bars the way to the search for material causes。 He goes so far as to doubt whether fleshy fruits are an adaptation for the dispersal of their contained seeds。 （Loc。 cit。 page 102。） Writing as I am from a hillside which is covered by hawthorn bushes sown by birds； I confess I can feel little doubt on the subject myself。 The essential fact which Guppy brings out is that long…distance unlike short…distance dispersal is not universal and purposeful； but selective and in that sense accidental。 But it is not difficult to see how under favouring conditions one must merge into the other。
Guppy has raised one novel point which can only be briefly referred to but which is of extreme interest。 There are grounds for thinking that flowers and insects have mutually reacted upon one another in their evolution。 Guppy suggests that something of the same kind may be true of birds。 I must content myself with the quotation of a single sentence。 〃With the secular drying of the globe and the consequent differentiation of climate is to be connected the suspension to a great extent of the agency of birds as plant dispersers in later ages； not only in the Pacific Islands but all over the tropics。 The changes of climate； birds and plants have gone on together； the range of the bird being controlled by the climate； and the distribution of the plant being largely dependent on the bird。〃 （Loc。cit。 II。 page 221。）
Darwin was clearly prepared to go further than Hooker in accounting for the southern flora by dispersion from the north。 Thus he says： 〃We must； I suppose； admit that every yard of land has been successively covered with a beech…forest between the Caucasus and Japan。〃 （〃More Letters〃； II。 page 9。） Hooker accounted for the dissevered condition of the southern flora by geographical change； but this Darwin could not admit。 He suggested to Hooker that the Australian and Cape floras might have had a point of connection through Abyssinia （Ibid。 I。 page 447。）； an idea which was promptly snuffed out。 Similarly he remarked to Bentham （1869）： 〃I suppose you think that the Restiaceae； Proteaceae； etc。； etc。 once extended over the whole world； leaving fragments in the south。〃 （Ibid。 I。 page 380。） Eventually he conjectured 〃that there must have been a Tertiary Antarctic continent； from which various forms radiated to the southern extremities of our present continents。〃 （〃Life and Letters〃； III。 page 231。） But characteristically he could not admit any land connections and trusted to 〃floating ice for transporting seed。〃 （〃More Letters〃； I。 page 116。） I am far from saying that this theory is not deserving of serious attention； though there seems to be no positive 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