Spkight. — The. Posf-r/lnrial Climate of ('aiitrrlnin/ . 417 



followed the. rain across the main divide, and the fact that this tree out of 

 all the rain-forest trees of Westland has done so is really very striking. 



Judging from the rainfall records kept at the Bealey, where the usual 

 amount for the year averages about 100 in., and has reached as much as 

 136 in., the rainfall of the Upper Rakaia Valley, which is exactly similarly 

 placed as regards the main range and the direction of the rain-bearing winds, 

 must certainly approach, if it does not exceed, 100 in. per annum. The 

 climate is decidedly moist and the drainage is good, and under these favour- 

 able conditions the totara occurs so plentifully in parts of the district that 

 it virtually excludes other forest-trees. 



These fac«ts seem at variance with the xerophytic-adaptation structure 

 exhibited in the leaves of the tree ; but this is one of the many cases which 

 have been pointed out by Dr. Cockayne where there is a marked discrepancy 

 between the actual structure and the structure one would expect the plants 

 to show judging from their habitat alone. In his " Notes on the Subalpine 

 Scrub of' Mount Fyffe " (Trans. N.Z. Inst., vol. 38, p. 373, 1906) he says, 

 " The amount of xerophylly in many New Zealand plants is by no means 

 a measure of their adaptation to present environment, but is more likely 

 a survival from a former geological period when xerophytic conditions 

 were more widespread." This opinion is a very important one from a 

 geological as well as from a botanical point of view, and it agrees with that 

 of Dr. L. Diels, quoted in Dr. Cockayne's " Plant Geography of the Wai- 

 makariri" (Trans. N.Z. Inst., vol. 32, p. 122, 1900). Dr. Cockayne's state- 

 ment about the xerophylly of New Zealand plants probably applies to the 

 totara, though it is no doubt possible that the advantage of possessing 

 a moderately xerophytic structure would aid it in its stioiggle with other 

 plants under increasingly dry conditions, and therefore may explain its 

 importance as a forest-tree in the forests which grew formerly over the 

 somewhat arid regions on the east coast of this Island. 



The date of this former forest-extension is fixed as being certainly post- 

 glacial, since the remains are commonly found in locahties which must 

 have been covered with ice, according to the most conservative opinions as 

 to the extent of our former glaciers ; and it must certainly have been pos- 

 terior to the great glaciation postulated by Professor Park, as the region 

 where these logs now occur in Central Otago was, according to him, covered 

 with a great ice-sheet. It is possible, however, that, as the glaciers retreated 

 from their furthest extension, the forest estabhshed itself fari passu on 

 the areas left free by the ice, just as they are now doing in the case of the 

 Franz Josef Glacier. The space of time taken for the gradual extension 

 of such a forest over regions swept bare of soil by the glaciers must have 

 been enormous, and if there has been a succession of forests, as suggested 

 by some observers, then the time must have been very great indeed. 



The question of the extent of these forests and the conditions under which 

 the totara grows have been gone into somewhat at length because, in my 

 opinion, it is possible to make the deduction that when the forests esta- 

 blished themselves the conditions must have been much different from 

 those obtaining now. It has been just stated that the forests have ex- 

 tended over areas which in Pleistocene times were covered with ice, and 

 were probably dry and steppe-like. Before they could do this the chmate 

 must have changed, as the New Zealand rain forest requires a moist climate 

 for its growth. This conclusion seems to agree with those deduced from 

 other observations. I must explain, however, that this conclusion is merely 

 U— Trans. 



