34 FUEGIA AND TASMANIA, 



essential details as small flowers and narrow medullary rays 

 should have been also evolved similarly on the two lines. 

 As the Fuegian and Tasmanian beeches are so very close 

 to one another, it would simplify matters greatly if we 

 could assume an east and west distribution of the Notho- 

 fagus subgenus after it had been evolved. 



Besides the similarity of structure, other features lend 

 weight to this direct continuity. Some- of the beeches of 

 Fuegia are infested with a unique fungus parasite, Cyttaria, 

 the onlv relative of which is found on the beech ot 

 Tasmania. Here, again, though it would be convenient 

 to assume that the closely related beech with the equally 

 closely related parasite must indicate a direct migration 

 along a laud connection, such a bridge may have been just 

 as probably subequatorial across the Pacific as subantarctic. 



The strongest evidence in favour of a high latitude land 

 connection is to be found in the presence of deciduous 

 beeches in both Fuegia and Tasmania. It is generally 

 taught that the deciduous habit is acquired by plants 

 through being subjected to regular dx"y periods. In many 

 places in the tropics where once a year thci-e is a dry 

 season, the trees save themselves from fatal transpiration 

 by shedding their leaves. Plants growing at a high latitude 

 are subjected to physiological dryness in the winter because 

 the water in the soil, being fi'ozen, is incapable of being 

 absorbed. It is assumed that the many deciduous trees of 

 tiie northern temperate zone acquired their habit as an 

 adaptation to such conditions, and have retained the 

 custom, though now living under a much less severe climate. 

 It is singular, if this explanation be correct, why it is not 

 customary for shrubs which live at a high altitude, where 

 the winter soil is always frozen, to have acquired the same 

 habit. It is, perhaps, more probable that the deciduous 

 economy has been thoroughly fixed upon trees growing 

 within the polar circle, where a complete absence of 

 effective light for many months has rendered the winter 

 shedding of leaves and rapid exposure of young foliage 

 in the returning spring, features of vital importance. If 

 such is the case, then we must consider the evergreen 

 beeches of Fuegia, New Zealand, and Tasmania to be 

 normal temperate trees, but the deciduous beeches of Fuegia 

 and our Fafjiis Gunnii to be species that have acquired the 

 deciduous habit by a comparatively recent evolution within 

 the Antarctic circle. If for this reason we do sufficient 

 violence to topographical ideas of the Earth as to demand 

 an extension of Fuegia and Tasmania to Antai'ctic, we 

 c^rtaiuly need not be too modest to claim the probability 

 of their direct connection. 



