Wall. — ^Ranunculus paucifolius T . Kirh. 97 



more violently and continuously upon it, the plants might all be buried, 

 as some of them no doubt have been. On the other hand, if the supply 

 of material deliverjed into the basin should diminish and finally cease 

 altogether, no doubt the closed tussock formation which now covers the 

 south-west portion of it would gradually invade the whole, and Ranun- 

 ciilus paucifolius would die out. This, it would seem, must ultimately 

 happen. 



The area has for many years been open to stock and rabbits, but they 

 evidently do not care for the plant, otherwise it would have perished long 

 ago. There are plenty of rabbits now in and about the basin. The 

 openness of the formation has no doubt protected the plant from destruction 

 by fire, a great and very real danger in New Zealand. 



Influence of Slopes. — The fact that it is confined to the easier slopes — 

 almost to level ground — is also of very great significance. Among its 

 associates, for instance, Lepidium sisymbrioides and Myosotis decora easily 

 maintain themselves upon very steep slopes, and consequently these plants 

 are quite widely distributed, occurring, in the immediate neighbourhood, 

 upon the limestone slopes at and near the junction of the Porter and Broken 

 Rivers, and upon those of the Whitewater River and of the Upper Porter 

 or Coleridge Creek, whereas Ranunculus paucifolius, by reason of its 

 apparent inability to grow except upon easy gradients, is debarred from 

 these areas, where every condition which it requires is to be had except 

 this one, and can maintain itself only within the very limited basin where 

 it is presumably doomed ultimately to perish. 



Limestone Soil. — When it is said that the plant can exist only in lime- 

 stone soil, it is not denied that it might live, if transplanted or sown, in 

 some other soil ; but the assumption is that in any other soil, if if can 

 live at all, it cannot compete with the ordinary vegetation of that soil : 

 it could live, that is, only under artificial conditions and when protected. 



Relation to Geological Problems. 



We may now consider what conditions are indicated as most probable 

 in the remote past of this community in general and of R. paucifolius in 

 particular. 



It seems inconceivable that the plant should have " originated," 

 established itself, and subsequently maintained itself for countless ages, 

 all within the narrow limits of its present distribution, and the first 

 condition requisite for its establishment would be the existence of a very 

 much larger area of continuous Tertiary limestone strata than is now 

 to be found anywhere in New Zealand. 



This area need not have been — and, indeed, could not have been — one 

 continuous sheet of limestone beds covering the whole of the district within 

 which the isolated fragmentai;y remnants now exist. But the inference 

 here drawn from the existence of this whole calciphile unit, and of Ranun- 

 culus jmucifolius in particular, is that these beds must once have been more 

 extensive arid more nearly continuous than they are now. The ancestral 

 Ranunculus may well have existed upon soils of pre-Tertiary origin and 

 developed there its xerophytic characters, while one form of it established 

 itself especially upon the limestone, developed characters accordingly, and 

 ultimately become virtually incapable of maintaining itself elsewhere. 

 This is, at any rate, one' hypothesis which seems to fit the facts. But the 

 exact sequence of events can here, in the nature of things, be only a matter 

 of conjecture. 



4 — Trans. 



