• diffidence. As it is well established that the occurrence of silky hairs in great quantity is a xerophytic phenomenon,^* it might be suggested that this character in S. saxifragoides is of climatic origin. The Port Hills, upon which S. saxifragoides flourishes, are nowhere higher than 1,800 ft., and most of the seven or eight high points upon them are between 1,500 ft. and 1,800 ft. in height; while the Akaroa peaks are on the average about 800 ft. higher than this, and Mount Herbert just exceeds 3,000 ft. As a consequence, the rainfall on Banks Peninsula proper is, and presumably has been for ages, considerably greater than on the Port Hills, the annual rainfall at the Convalescent Home station on the Port Hills being 25–52 in., while that of Akaroa is 44–72 in. There is no geological evidence to show that, since the formation of Lyttelton and Akaroa volcanic areas, Banks Peninsula proper and the Port Hills have not always stood in the same relation to one another as at present in respect of altitude, rainfall, and climate generally, though when the level of the whole was higher than at present, as it once undoubtedly was, the rainfall upon the Port Hills might have been more greatly reduced, relatively, than that upon Banks Peninsula proper. It might thus be argued that the drier climate of the Port Hills has directly determined the development of S. saxifragoides as above outlined. If this were the case we should expect to find similar forms developed in other dry localities, but it is doubtful whether any equally suitable situation exists within the limits of distribution of S. lagopus. If the Port Hills form a unique locality in this respect one could understand how S. saxifragoides has such a narrowly restricted range.

Upon this theory S. saxifragoides and S. lagopus would be classed as two varieties of the same plant, differing only in the degree of efficiency reached, under stress, in the development of their xerophytic apparatus.

Presumably, also, the other peculiarities of these two plants, such as the woolliness of the rootstock and petiole, might be assigned to the same general cause. Presumably all the six structures above described upon the leaf of S. lagopus, except, perhaps, the marginal glandular structures, would perform a similar function, though attention has here been confined to those two which characterize the upper surface of the blade of the leaf.

I desire to express my acknowledgements, first, to Dr. L. Cockayne, F.R.S., to whom I owe the original suggestion of this paper, and without whose kindly encouragement and invaluable aid the work could not possibly have been carried out by me; also to Miss E. M. Herriott, M.A., assistant in the Biological Laboratory, Canterbury University College, who made the microscopical examinations of the various structures and described them (as above) in the most able manner; and, finally, to Mr. R. Speight, M.Sc., F.G.S., Curator of the Canterbury Museum and Lecturer in Geology at Canterbury University College, who supplied the geological history of Banks Peninsula here given, and also very kindly photographed for me the plants of Senecio lagopus on Mount Sinclair (Plate XIII).