_ ON THE 
GEOGRAPHICAL BOTANY OF NEW ZEALAND. 
EXPLANATORY OF A SERIES OF Essays BY 
SIR DAVID MONRO AND MESSRS. TRAVERS AND BUCHANAN. 
BY JAMES HECTOR, M.D., F.R.S. 
(Plate V.) 
[Read before the Wellington Philosophical Society, 15th September, 1868.] 
Iw communicating the following essays, I will take the opportunity of 
explaining briefly, by a single example, the chief physical peculiarities which 
regulate the distribution of the vegetation in the South Island. 
The accompanying diagram (pl. V.) is an ideal section across the island, 
between latitudes 40° 30' and 46°30'S. The greatest altitude met with in such 
a section will be 10,000 feet, but the mean elevation of the ridges that 
connect the various summits is barely 5,000 feet, while in these occur breaks, 
r “passes,” in the mountain chain, which, by permitting the passage of the 
western winds, give rise to local modifications of the flora at the points 
where they lead out on the eastern slope. The best known of these are the 
pass from the head of the Wanaka Lake, by which Dr. Haast crossed to 
Jackson Bay; and the Greenstone Pass, leading from the Wakatipu Lake to 
Martin Bay. Another pass, only a few miles in length, crosses the narrowest 
part of the Southern Alps, between the head of the sounds and arms of 
Te Anau Lake 
These breaks in the mountain chain have all about the same altitude of 
less than 2,000 feet above the sea level, which is sufficiently low to admit of 
the transfusion of many species of plants. 
From the fact that these passes follow longitudinal valleys with a 
succession of short gorges at right angles to their general course, and do 
not coincide with straight transverse depressions, the influence which in 
the latter case they would have exercised on the climate of the interior is 
greatly reduced ; nevertheless, the mild and genial climate that is experi- 
enced in the neighbourhood of the Wanaka and Wakatipu Lakes, is to be 
attributed, in a great measure, to the existence of these deeply-cut notches 
in the mountains. 
