Cockayne. — Ecological Studies in Evolution. 5 



treatment are Olearia Haastii Hook. f. and 0. oleifolia T. Kirk (p. 290), 

 Ranunculus Sinclairii Hook. f. and R. gracilipes Hook. f. (p. 18), and 

 Poa seticulmis Petrie and P. pusilla Berggr. (p. 905). 



6. Veronica buxifolia Benth., as originally denned, probably referred to 

 a quite definite set of individuals Even by Cheeseman (pp. 522, 523) the 

 species is spoken of as a " plant," and not as a varying series of forms. 

 Further, the species is defined as " erect," and but one variety is allowed. 

 In point of fact, however, the " species " includes three distinct growth-forms, 

 at any rate, two of which, the prostrate, and the low, erect, sparingly branched, 

 are shown in Plate II, fig. 1. The var. odora T. Kirk (patens Cheesem.) 

 is of the ball-like growth-form. In this example, then, a taxonomic species 

 includes plants belonging to at least three absolutely distinct biological categories. 

 And, in addition, it is highly probable that a dozen or more distinct true- 

 breeding entities might easily be separated from the heterogeneous mass of 

 individuals known as V. buxifolia. 



7. Many varieties are of a quite different physiological value to others. 

 Some, as in cases 1, 2, and 6, reproduce themselves true from seed. This 

 I have definitely proved in a number of instances ; they are, in fact, true 

 elementary species. Others, again, are merely environmental (unfixed ephar- 

 monic)* forms, such as are dealt with further on, of which notable examples 

 are the var. prostrataf Hook. f. of Leptospermum scoparium Forst. (p. 160), 

 the var. rhombifolius% Hook. f. of Ranunculus pinguis Hook. f. (p. 12), and the 

 var. pauperatus§ T. Kirk of Rubus cissoides A. Cunn. (p. 125). Finally, other 

 varieties represent a series of forms regarding the stability of which nothing is 

 known, but which are supposed, without any sufficient reason, to be unstable. 



Without going into further details, it is evident that the species of New 

 Zealand taxonomists are. rather the creation of man than of Nature. In 

 saying this I am not hypercritical. The main object of a flora is to enable 

 a plant to be readily identified, and this, from the very nature of the case, 

 demands a more or less artificial classification. Where such precise and 

 copious information as to variation is given as in Cheeseman's most careful 

 and exact work there need be no mistake, and the worker in the field knows 

 exactly what he may expect. But, as a rule, writers on evolution have 

 quite neglected to distinguish between taxonomic and physiological species, 

 which latter alone are their concern. !| 



Although breeding-experiments can alone decide as to fixity of form, 

 ecology should tell something. If a certain set of individuals remain 

 unchanged over wide areas, so far as their specific marks go, and under 

 varying conditions, it may be assumed with tolerable confidence that they 

 reproduce their like, and are therefore species, elementary or Linnean, as 



* Such forms are called by Massart " accomodative," in contradistinction to " adap- 

 tive " — i.e., specific and hereditary. Regarding taxonomic varieties, the same author 

 writes, " Malheureusement on ne peut pas toujours se tier aux travaux de eystematique 

 pour distinguer les accomodations des variations proprement dites," and he cites the 

 example of Polygonum amphibium, with its varieties nutans, terrestre, and maritimum, all 

 of which are simply accomodative states. (1910, pp. 9, 10.) 



t See Cockayne, 1909, p. 16. 



% See Cockayne, 1909a, p. 201. 



§ See Cockayne, 1901, pp. 293, 294. 



|| O. F. Cook's remarks are worthy of consideration (1907, pp. 362, 363): "The 

 difficulty of defining the term ' species ' has arisen mostly from the fact that the 

 phenomenon is a physiological one, whereas the general supposition has been that it 

 is morphological. . . . For evolutionary purposes a species is a group of inter- 

 breeding organisms ; nothing more is required, nothing less will suffice." 



