SriOKUlT, Cot'K.WXK, JiAl.NC. — M'lu/// J rro /rs >,//'/ // l)i<trirf. 347 



3. THE PLANT KORMATIONS. 

 (A.) Gexkral. 



Here tlie term " formation " is used in the generic sense indicated by 

 Warming (1909, p. 140), tlie fell-field, for instance, being a portion of the 

 general fell-field of New Zealand and of mountains in other parts of the 

 world, while the associations are local, and, though made up of similar 

 growth-forms to those of the formation elsewhere, dift'er in their floristic 

 components. Suhassociations are smaller communities within the asso- 

 ciation, and within these latter again may be groups of species. Finer 

 distinctions still could be made, but for such a most careful analysis of 

 the vegetation would be required, and this is not demanded or desirable in 

 New Zealand so long as the broad features of so much of the vegetation 

 remain unknown. To estimate rightly the limits of certain associations, 

 and especially subassociations, is not so easy as might be thought. 



It must also be pointed out that the study of vegetation should be 

 dynamic, and not static. Associations are not independent creations, but 

 each has its life-history — its birth, its youth, its manhood — and in certain 

 instances its evolution may be seen in progress, especially where there is a 

 rapidly changing topography, as on a river-bed,* or where rock changes to 

 fell-field by way of shingle-slip. 



The same climax formation may come into being from different begin- 

 nings, or may be the result not of progression, but of reversion. Not- 

 withstanding that an association is part of a series, it is a distinct association 

 for all that, and may be just as much a feature of the landscape as a climax 

 association, from which it differs only in its much shorter life. 



(B.) Steppe-climate Formations. 



(u.) THE STEPPE SERIES. 



(1.) General. 



Steppe, in one or other of its phases, occupies the greater part of the 

 Arrowsmith district up to an average altitude of perhaps 900 m., though 

 this is somewhat exceeded in the east. Above it gives place to fell-field or 

 scrub, according to the rainfall. There is both edaphic and climatic stepjje, 

 as also combinations of the two. 



The term " steppe " Avas first used for the New Zealand plant formation 

 in 1908 by Cockayne, when dealing with the volcanic plateau in the North 

 Island ; previously the same author had used the term " meadow " for this 

 and other xerophytic formations of grasses and herbs. Laing and Black- 

 well, however, in 1906 had already shown that " tussock country," as they 

 called it (1906, pp. 3, 4), was a vegetation-form of a different type from 

 meadow proper.f How nearly related the New Zealand steppe may be 

 to that of Warming (1909, pp. 281-88) is another matter. Certainly the 

 rainfall and number of rainy days is much greater than Warming gives 

 for a steppe climate ; but it must be borne in mind how greatly a heavy 

 rainfall can be discounted by frequent high winds plus a non-retentive soil. 

 The formation also seems related to Warming's " chersophyte vegetation," 



* See Part I re topography of a river-bed. 



I " Grass stepjie is found where the rain i.s moderate in amount, but falls only a 

 few days in the year ; grass steppe as a rule can be utilized for cultivation without 

 artificial irrigation " (Warming, 1909, j). 274). 



