Wall. — Ranunculus paucifolius T. Kirk. 103 



would disappear and leave it as it liad been when the drought began. The 

 five species here treated as a collective group would represent varying 

 degrees of " adaptation " of this kind, and none of them is a true species, 

 or even a naicrospecies, unless it already possessed its distinguishing specific 

 characters at the beginning of the period. In this respect Ranunculus pauci- 

 folius is like any of the others of the group, and it is impossible for us to 

 tell whether it originated from the same ancestral form with them or was 

 already a true species when the stress of drought came upon it. Its 

 " adaptation " to a limestone soil is thus most probably not a specific 

 character, but an adaptation of the unstable kind which may disappear as 

 soon as the need for it is withdrawn. The test of cultivation can alone 

 decide this point. 



It would be beyond the scope of this paper to discuss all the difficulties 

 which stand in the way of a full acceptance of these propositions. But 

 it may be said that the words " however small " (" Species-making changes 

 occur by leaps and bounds, however small ") seem to imply a very great 

 concession. Changes of the nature of " adaptations " to new conditions 

 are not denied (De Vries, 1912, p.. 579). " It is clear that we may call all 

 these changes adaptations to new conditions. But then we must concede 

 that these adaptations depend upon characters which were inherent in the 

 species before it arrived in the new environment." And, as very small 

 changes may be due to true mutations, there seems to be no very great 

 difierence between the opposing views. It is admitted that imder new 

 conditions a species may change very greatly and appear to become quite 

 a different species, and it is admitted that under new (as under any other) 

 conditions a species may acquire very small new characters by mutation 

 and so become a new species. Is it not possible that the " state of 

 mutability," whose causes have hitherto remained obscure, may be induced 

 by the impact of new conditions and the demands of a new stress ? No 

 very great adjustment seems necessary to reconcile this view with that of 

 De Vries. He says that plants may change and adapt themselves gradually 

 to new conditions, but no new species can originate in that way ; changes 

 so induced are not " mutations." It may be suggested, on the other hand, 

 that possibly new characters, due to " mutations," may be acquired by the 

 plant as a direct response to Nature's ultimatum, " Change or die ! " 



Conclusions. 



1. The original description of the species by Kirk is not quite accurate. 

 The number of the leaves is not abnormally small, being frequently 5 and 

 may be as many as 9. The style, when the achene is ripe, is curved, 

 not straight. The flowering-period is late October and November, not 

 December. The petals number 5 to 8. 



2. It is one member of a xerophytic plant community, or association, 

 of very ancient origin, and is specially adapted, like some others of that 

 community, to live upon a limestone soil, or, rather, debris formation. 



3. Though its habitat is now, so far as is known, extremely restricted, 

 it must formerly, with its associates, have been distributed over a far more 

 extensive area of Tertiary limestone beds. This conclusion supports that 

 reached by Speight (1915, p. 345) upon quite dift'erent evidence. 



4. It is the product of a period of drought or steppe climate, which 

 directly caused the development of its xerophytic characters ; and in this it 

 resembles the other members of the community to which it belongs, one 

 which was fornaerly, in all probability, far richer in species, and perhaps 

 even in genera, than it is now. 



