Cockayne. — Ecological Studies in Evolution. 31 



most important of these is V. Hectori Hook. f. (a "whipcord veronica") 

 x V. pimeleoides Hook. f. (a small glaucous-leaved straggling rock-plant with 

 blue flowers), and the result is a plant said to be identical with or 

 near to V. epacridea Hook. f. If this is true, it opens up much suspicion 

 as to the validity of many species of the genus in New Zealand, and, at 

 any rate, in the case of variation in general, as some of the species are 

 gynodioecious,* hybridism may be the simple explanation. 



Mr. Mclntyre, who had charge of the famous collection of New Zealand 

 plants of the late Mr. H. J. Matthews, raised a good many hybrid forms 

 of Celmisia, all of which appeared to have the so-called C. verbascifolia^ as 

 one of the parents. I have seen a Celmisia on Jack's Pass which was most 

 likely a hybrid between C. spectabilis and G. coriacea. Also, C. mollis 

 Cockayne is possibly of hybrid origin, with C. spectabilis as a parent. In 

 short, hybridization may account for some of the variation in Celmisia. 

 Acaena, again, is a very variable genus, which suggests hybridization. 

 Buchanan was the first to call attention to this matter, and he described 

 a supposed hybrid between A. Sanguisorbae Vahl. and the introduced 

 A. ovina A. Cunn. (1871, p. 208). Kirk reduced this to var. ambigua of 

 A. ovina, notwithstanding that the inflorescence is altogether different from 

 that of that species. Bitter (1911, pp. 297-321) describes fifteen hybrid 

 forms of Acaena, illustrated by figures of leaves, in which varieties of 

 A. Sanguisorbae, A. microphylla, and A. glabra are parents, one or the other. 

 Tnese forms have originated spontaneously in the Bremen and other Con- 

 tinental botanical gardens. Bitter is convinced they are true hybrids, and 

 that the only question that can be raised is as to the parentage that he 

 suggests for them. A full account is given of each form. 



I have seen, judging from the capsule, what appear to be wild 

 hybrids between Phormium tenax Forst. and P. Cookianum Le Jolis. 

 A good deal of the variation in P. tenax may be due to hybrid ele- 

 mentary species, for that it is made up of many such entities seems very 

 probable. J 



Melicope Mantellii Buchanan is supposed by some to be a hybrid 

 between M. simplex A. Cunn. and M. ternata Forst. (see Kirk, 1889, p. 118). 

 I have proved that it comes true from seed, and in the absence of experi- 

 mental evidence it is quite as reasonable to suppose it is an elementary 

 species connecting M. simplex and M. ternata. All three have ternate 

 juvenile leaves ; M. ternata remains at this stage but with much larger adult 

 leaves, M. Mantellii has both simple and ternate leaves in the adult, and 

 M. simplex is a divaricating shrub when adult with simple leaves. 



VII. The Struggle for Existence. 



Plant-ecologists have many opportunities for observing various phases 

 of the struggle for existence. They have also some opportunity of judging 



* I am indebted to Professor I. Bayley Balfour, F.R.S., for calling my attention 

 to this phenomenon in our veronicas, which he was the first to discover. I had pre- 

 viously wondered why certain species in my garden never produced seed, and others 

 very little, and had ascribed it to the absence of the proper pollinating insect. How 

 far the phenomenon is present in wild plants has not been as yet ascertained. 



t Probably C. verbascifolia Hook. f. = C. Brownii Chapman. 



% The Chatham Island form, with its thin broad leaves, is distinct, so far as I know, 

 rom any of the mainland forms. 



