96 Transactions. 



Ecological : Main* Problems involved. 

 General. 



These problems may be thus stated : How are we to account for the 

 survival, in an exceedingly limited area, of a very special and peculiar 

 formation, and in very limited numbers, of a plant, which is obviously 

 adapted to a climate very different from that of the present time, which 

 reproduces itself only by seed, not vegetatively, and that only in a very 

 sparing manner, and which apparently can exist only upon a kind of 

 soil occurring only in limited areas separated from one another by^ great 

 distances ? 



Apart from geological history several considerations may here be given 

 as bearing upon the main problems. 



Reproduction and Distribution of Seed. — The achene, on dropping off, 

 no doubt falls into the soil and is moved by the wind, as the surface of the 

 debris is quite unstable, most of the plants being actually buried in it above 

 the rootstock. It is remarkable that none of the plants of this association 

 is a " traveller." The seed of all is presumably distributed in the same 

 way — by the action of the wind in shifting the soil ; none of them is provided 

 with a pappus or coma ; no composite plant except Raoulia australis enters 

 into the unit. Epilohitim gracilipes and Senecio Monroi var. deniatus, 

 which occur on the steep slopes and rocks above the basin and have 

 seeds specially adapted for carriage to a distance by the wind, are absent 

 altogether from the flatter portions of the area. 



Instability of Soil. — The wind is always bringing fresh debris into the 

 basin, and is always stirring and shifting all that part of the surface which 

 is entirely or nearly bare. As .the rocks are now always rapidly crumbling, 

 and no doubt have been in the same state for a very long period of time, 

 it follows that they must formerly have been much larger than they are 

 now ; therefore they must formerly have set free annually a much larger 

 amount of material, and therefore the superficial area of unstable debris must 

 formerly have been much greater. But in recent times the area of bare 

 debris could never have been really extensive, as the accumulation of it 

 would hardly be possible under present conditions except within the enclosed 

 space of the basin. However, in some much older age it may be imagined 

 that a much greater area lying eastward of the small basin might during 

 a period of steppe climate or drought become a semi-desert, mainly of this 

 debris, supporting a calciphile and xerophytic flora, in open formation, of 

 such individuals and in such disposition as we now see within the enclosed 

 and protected area only. 



Struggle for Life. — ^As Warming (1909, p. 256) observes of fell-field in 

 general, the typical xeroph}i;ic plants are so thinly distributed that they 

 do not interfere with one another nor compete with one another. It is 

 so here, and it is so upon the steep shingle-slopes of the dry eastern 

 mountains of the neighbourhood. Ranunculus Haastii, for instance, is 

 exactly like R. paucifolius in this respect. Only a certain small number 

 of plants grow within a given space, when, so far as one can see, an 

 infinitely greater number might grow there without in the least incon- 

 veniencing their neighbours. 



Thus Ranunculus paucifolius has not been threatened with extinction 

 in this manner. It seems, however, to have had to face two other dangers 

 in recent times. On the one hand, if the surface upon which it grows 

 were for any cause to become still more unstable, and the wind to act 



