THE VICTORIAN NATURALIST. 



ability to migrate is for our question of the greatest im- 

 portance. 



We have therefore to look back to times long past and to hear 

 what geologists have to tell us about the Tertiary period, with 

 regard to which I quote Prof. E. A. David : — " We would here 

 like to emphasize the opinion that it is out of the question to 

 refer either the Hedley Tarn glacial epoch or the Lake Mere- 

 wether glacial epoch of Kosciusko to Tertiary time. We are 

 strongly of opinion that these epochs belong to the Post Ter- 

 tiary. If, however, later examination proves that there was a 

 much earlier and far more extensive glaciation which affected the 

 whole of the Kosciusko plateau, and extended even as far down 

 as Lake Coolamatong, near Berridate (Plate VL) (about 2,500 

 feet above sea level), as one of us (Mr. Helms) thinks, it is quite 

 possible that this older glaciation may belong to Tertiary time." 



It is not, however, within the scope of a botanist to examine 

 the statements of geologists as to whether they are right or wrong. 

 Be it as it may, so much is certain that all the respective indica- 

 tions point to the fact that a glacial epoch extended during 

 Tertiary times over the greater part of the Australian Alps. 

 It is to us of less importance if Australia was visited by 

 only one glacial period (the Post Tertiary) or by two or 

 more of older ages, which each in its time of advance 

 must have caused a retreat of the flora to a climate more 

 suitable for them ; vice versa, at the retreat of the glacial 

 epoch the plants will have returned more or less to their 

 former territory. How often may have followed, in different 

 geological periods, a tropical vegetation on one of a sub-tropical 

 or antarctic character ; how often may have, under such circum- 

 stances, perished and disappeared our evergreen forests with their 

 lofty crowns ; how often may have mighty glaciers covered the 

 slopes of our valleys on which our present alpine vegetation has 

 finally settled itself. For our case only the most recent of the 

 glacial epochs in Post Tertiary time is to be considered, for mostly 

 through this the present character of our alpine flora has been 

 determined. 



Referring to this glacial epoch, the lowlands extending from the 

 Alps to the south at this time must have had a temperature which 

 was very similar to the one at present prevailing in higher alti- 

 tudes. On this tract of land a quite distinct flora has settled 

 itself, which again succeeded the preceding species, partly 

 succumbed or altered in their characters through the cold 

 temperature setting in with the glacial period. It was that flora 

 of which a great part now inhabits to-day our alpine regions. 



The extreme limit of the drift ice in the Southern Ocean lies 

 at present at about 50° S. lat. An advance of a few degrees 

 must have brought it in contact with the southern shores of Aus- 



