Ill 
Hybridism in the New Zealand Flora 
As for distribution the hybrids occur in the following plant- 
formations to each of which is attached the number found therein: 
rain-forest 25, subalpine herb-field and fell-field (taken together) 25, 
tussock-grassland 11, stony river-bed (lowland to montane) 10, sub- 
alpine-scrub 7, coastal scrub 7, and, in addition, 23 other formations 
also contain hybrids. 
Finally, the altitudinal distribution of the hybrids is: coastal 13, 
lowland 34, subalpine 39, lowland and montane (both) 19, lowland , 
montane and subalpine (all three) 2, montane and subalpine (both) 
21. 
An .accurate knowledge of the relative distribution of the alleged 
parental species is of prime importance. This can be conveniently 
studied in New Zealand proper 1 , owing to the comparatively narrow 
land-surface extending from north to south through nearly fourteen 
degrees of latitude 2 and the general proximity of lofty mountain 
ranges to the lowland belt. Thus, speaking of the distribution of the 
New Zealand flora in general, and commencing at the far northern 
limit of the North Island, certain species range more or less con¬ 
tinuously throughout the whole area, but a large majority have their 
respective northern and southern limits within the area. This 
depends, in the case of coastal and lowland species, partly on 
their relation to frost 3 . Now, amongst the different genera are many 
related species each with its distinct range; but, at definite points, 
some of these come together and extend jointly north or south for 
a certain distance. If the ecological requirements of such pairs of 
species are fairly equivalent they will, at times, occur side by side, 
and crossing then becomes possible, its frequency depending upon 
the time and duration of the flowering season, and their requirements 
in regard to cross-pollination. The latter has been but little investi¬ 
gated, but, as unisexuality is common and dichogamy apparently 
frequent, there are often opportunities for crossing. 
In certain instances intermediate forms appear in the first 
locality where the two species come together. The main cause of the 
1 This includes the North Island, the South Island and Stewart Island. 
The New Zealand Botanical Region also comprises the Kermadec, Chatham 
and Subantarctic Islands. 
2 Really the 34th parallel of South latitude lies Some 20 miles north of 
the North Cape and the 48th parallel some 30 miles south of the South Cape 
of Stewart Island. 
3 For a fuller account of plant-distribution in New Zealand see L. Cockayne, 
The Distribution of the Vegetation and Flora of New Zealand , Cawthorn Lecture, 
Nelson, N.Z., 1921. For the part relating to latitudinal distribution see 
pp. 12-16. 
