Cockayne. — Plant Geography of the Waimakariri. 99 



of the type species to which it is referred. Other species 

 vary simply through environment, and when such varieties 

 are grown side by side under the same conditions they become 

 indistinguishable. In such cases oecology.can assist syste- 

 matic work and check its results. Of late, botanists in 

 New Zealand have been much more ready than formerly to 

 admit closely related forms as good species, which certainly 

 seems a step in the right direction.* 



Only the angiosperms, gymnosperms, and pteridophytes 

 are here treated of. With these, many lower plants are, of 

 course, associated in the plant-formations as component and 

 often most important constituents, but an account of these 

 can only be undertaken by specialists. 



The country to be treated of includes all the land drained 

 by the Eiver Waimakariri and its tributaries, with the excep- 

 tion of those portions of Big Ben and the Malvern Hills which 

 form a part of its river-basin. 



To the following I beg to express my most hearty thanks : 

 Mr. D. Petrie, M.A., to whose splendid collection of Otago 

 plants I have had full access ; Professors A. F. P. Schimper, 

 K. Goebel, and A. Dendy, for assistance regarding litera- 

 ture ; Captain F. W. Hutton, F.R.S., who most kindly cor- 

 rected the geological details; Sir James Hector, F.E.S., and 

 Sir John Hall, K.CiM.G., for assistance regarding meteorology; 

 Messrs. T. W. Adams, John Deans, W. Cloudesley, J. Roun- 

 tree, S. Weetman, E. G. Staveley, manager of the Loan and 

 Mercantile Company, A. L. Taylor, of the Christchurch 

 Botanic Garden, and Mr. T. Douglas, manager of Mount 

 White Station, who have rendered me much valuable aid. 



Topography . 



With regard to the main features of the region under con- 

 sideration, we may make a primary distinction into lowland, 

 table-land, and mountain regions. 



Commencing with the lowland region, we find, near the 

 mouth of the river, extensive sand-dunes, which terminate at 

 the wide brackish lagoon formed by the river as it empties 

 itself into the sea. Formerly the river also flowed into the 

 sea more to the south, one channel, at any rate, going down 

 the present bed of the Avon.t 



The sand-dunes consist of two varieties — the recent, which 

 are in a very unstable condition, constantly moved by the 

 frequent high winds, and having the yellow-leaved Desvio- 

 schcenus spiralis as the leading plant ; and the older, which are 



* As to what is meant by the term " species," Komanes has written 

 at considerable length : see " Darwin and after Darwin," vol. ii., London, 

 1895, chapters viii. and ix., especially pp. 202-208 and 229-235. 



t See map facing p. 396, in Haast's " Geology of Canterbury and 

 Westland," Christchurch, 1879. 



