L. Cockayne and Foweraker. — Plant Associations at Cass. 167 



Western Soutli Island Botanical District, or, in other words, it lies just 

 beyond the influence of the excessive western rainfall. This is most plainly 

 reflected in the physiognomy of the vegetation, where, on the Cass side of 

 the River Waimakariri, the xerophytic grass-tussock form dominates the 

 landscape (see Plate XV, fig. 1) ; while on the other side of the river, only 

 some two miles distant, stands a vast dark mesophytic forest-mass with clean- 

 cut margin, hardly one tree standing out into the open grassland of the east. 

 Nowhere can a more striking example be seen of the direct efiect of climate. 

 The change in physiognomy is instantaneous ; there is no transitional phase. 



The matter of this paper is the outcome of a few visits to the area made 

 at different times by the authors independently of one another, and especially 

 of a recent brief stay at the station, when the various associations were 

 conjointly examined by the authors, and lists of the species hurriedly taken. 

 Unfortunately, the time available for observations was much too short, 

 while, owing to the season of the year (November), certain species were not 

 in bloom and could not be accurately determined. Therefore, this study is 

 limited to brief descriptions of the associations, and doubtless many species 

 have been omitted. In certain cases " var." is placed after the specific 

 name. This denotes that the species is an aggregate, and that the plant 

 referred to is one of the unnamed varieties of which the aggregate is com- 

 posed. On the other hand, " var." being absent does not mean definitely 

 that the species is a true entity. It means either that we think the species 

 may be a definite entity or else that we have no proof that it is an aggregate. 



The associations dealt with fall under the following heads : (1.) Forest, 

 (2) shrubland, (3) grassland, (4) swamp, (5) rock, (6) river-bed. This classi- 

 fication is obviously faulty, since it contains associations based some on 

 growth-forms and some on habitat ; but it is convenient, easy of appli- 

 cation, and can be readily used both by those visiting the station and for 

 phytogeographical purposes generally. 



Many of the associations are greatly modified at the present time through 

 the action of man, the chief modifying agencies being the grazing of sheep 

 and frequent fires. To a much lesser degree, partly also through the above 

 two factors, various foreign species of plants have gained a firm footing and 

 come into competition with the indigenous element. Much more important, 

 however, is the fact that the degree of frequency of the component species 

 of certain associations has been greatly changed, so that infrequent mem- 

 bers of the primitive association may now be of prime importance. But 

 it must be pointed out that, so far as ecological studies at Cass are con- 

 cerned, the introduced plants are now as much members of the associations 

 as are the indigenous species, and they must be equally considered. This 

 is especially important since a good deal of future research may have a 

 distinct economic bearing. This paper concludes with a list, quite incom- 

 plete, of the species belonging to the associations. Also, for the informa- 

 tion of those not conversant with the New Zealand flora, a very brief account 

 is given of the growth-form of each species. This, it must be pointed out, 

 refers solely to the plant as it grows at Cass, and has nothing to do with the 

 growth-forms of a species through its entire range, or with its commonest 

 form. 



(B.) THE ASSOCIATIONS. 



(1.) Forest. 

 In the immediate vicinity of the biological station forest is poorly repre- 

 sented. This is not on account of its destruction by fire, as in so many 

 parts of New Zealand, but because in the Eastern Botanical District, in the 



