160 Transactions. 



ance of the formation. The colour of the tussock is almost invariable 

 during the whole year, and there are no periods of specially rapid 

 growth. This latter, of course, is partly due to the fact that the leavea 

 are long-lived and do not die off each year, so that there does not seem 

 to be any special season for the maturing of the foliage. This almost 

 absolute uniformness of the general appearance of the tussock grassland 

 is one of its most striking features, and sharply marks it off from many 

 other types of grassland in New Zealand. 



It has been previously shown that the elements of montane tussock 

 grassland are at most only sparingly grazed upon. It is thus really 

 not peculiar that the dominant physiognomic plants should have retained 

 their position in the formation. In grasses it does not appear unusual 

 that the species least eaten are the most likely to increase. Thus in the 

 pumice soil of the Volcanic Plateau sowings composed of about equal 

 quantities of cocksfoot and florin (Agrostis stolonifera L.) become at the 

 end of a few years almost pure florin pastures. In this case the cocksfoot 

 is kept eaten down, while the florin is rejected. In other cases, however, 

 the grass fed on attains the mastery over that not touched, as is seen in 

 artificially induced pastures of one or other of the forms of Danthonia 

 jnlosa R. Br., where originally the lowland tussock was the more im- 

 portant constituent. In such cases, however, the palatable plant that 

 increases must be better fitted for the conditions than are the species 

 which it displaces. 



Before the advent of pastoral occupation, there is no doubt that 

 many areas which are now typical montane tussock grassland were occu- 

 pied with associations that were gradually turning in course of time 

 into ordinary tussock association. Thus, for instance' Discaria thickets 

 were probably more numerous than at present, occupying young con- 

 solidated fans and other features of the land-surface that were of 

 comparatively recent origin. Burning has had the effect of more or 

 less eliminating this scrub, and has induced the climax associations of 

 tussock grassland to become developed more rapidly than would have 

 otherwise been the case. 



In the neighbourhood of Cass the main feature of the grassland is 

 the very large amount of Poa Colensoi. I am inclined to think that 

 this grass was not particularly important in the primitive vegetation, 

 but has increased enormously since the advent of pastoral operations. 

 Its prevalence is especially noticeable on areas formed of material com- 

 paratively recently water-transported, such as fans, young river-terraces, 

 and the like. On the hillsides, on the other hand, FeHuca novae- 

 zealandiae is easily dominant, and the blue tussock {Poa Colensoi) is- 

 quite a subsidiary element of the vegetation. The last-named grass also- 

 appears to be on the increase where burning has been extensively prac- 

 tised. Being smaller than the fescue tussock, it is probably less affected 

 by summer burns than is the taller grass. A notable feature near Cass 

 was its generally uneaten appearance, which was certainly indicative 

 that this grass is not favoured by stock. Of course, it must be recog- 

 nized that Poa Colensoi is an aggregate species, and it is possible that 

 certain forms are more palatable to stock than are others. Another 

 characteristic feature of the Cass tussock-land is the almost complete 

 absence of the true blue grass, Ar/ropyron scahrum. In general, I should 

 say that in the upper Waimakariri river-basin the main effect of pastoral 

 operations on the indigenous vegetation has been the more general 

 domination of the tussock growth-form element in the tussock grassland 

 and the reduction in frequency of occurrence of shrubby plants, due to 



