Grass and Herb Formations. ; 231 
plants of both classes, while grass-tussock is frequently a common feature of 
herb-field. Still the distinction is ecologically sound, because dominance of 
grass in primeval New Zealand denotes a fat stronger PR than does that 
of herbs and the two opposing formations, steppe”) and herb-field, are essen- 
tially expressions of climate. On the other hand, the distribution of fell-field 
is, in part, due to edaphic causes, and the formation might with some pro- 
priety, but much less convenience, have been dealt with under the heading 
of debris. 
Although the formations under consideration are each of a definite eco- Er 
logical character throughout their range in New Zealand, there are many dif- 
ferent combinations of species in passing from N. to S., or from dry to wet 
areas. There are also often great differences between mountains in close 
proximity, so that it is impossible, in a brief account, to include all details, 
‚even were such known. Here, at best, a general and broad view is attempted, 
especially such as may bring out the salient features both with regard to dis- 
tribution and ecological distinctions. 
db. Tussock steppe. 
The general remarks as to grassland in Section ıı apply here also, except 
that tall steppe is not specially, as in the lowlands, a mark of sour ground 
but rather of higher altitude. The various associations with few exceptions 
_ are far from being virgin, but the number of introduced plants is far less than 
in the lowlands. Frequent burning and overstocking, however, have in certain 
‚localities, especially the North Otago district, changed the formation altogether ; 
eng it into actual desert. Be 
1 Bi jation) 
1. Low tussock steppe (Poa-Festuca tussock-g BER. 
This formation up to an altitude of 600 m, or more, 2 already bien de “ 
tion. ‚At above that. altitude certain 
