Cockayne. — Pla}it Geography of the Waimakariri. 123 



formation of a dry easterly steppe region, where the survivors 

 of the forest had become modified, and assumed the structure 

 and physiognomy of desert plants. I shall refer to this again 

 when treating of these plants, but I think the observations 

 recorded in this paper show a climate in the east quite 

 sufficient even at the present day to account for structure so 

 xeropbilous as that of Carmichaelia 7iana. 



That these adaptations are really for the purpose of resist- 

 ing drought, and that they have been evoked by a dry climate, 

 has been more or less proved in certain instances. Goebel 

 was the first to show that Veronica ciqyressoides, when culti- 

 vated in moist air, produced true leaves, with stomata on both 

 surfaces, and which were strictly of an extreme hygrophilous 

 type.* At about the time of the publication of this experiment 

 Mr. E. Brown was engaged in similar experiments here. He 

 cultivated pot plants of Baoulia temiicaulis, Ozothamnus 

 microphyllus, and Veronica arvistrongii in his greenhouse, the 

 glass of which was not shaded, with the result that all pro- 

 duced leaves differing much from the wild plants.! I have 

 repeated Goebel's experiment, and find that Veronica ctipres- 

 soides is so unstable that it will produce these reversion leaves 

 in six weeks' time when cultivated under a bell glass and kept 

 constantly moist. Under the same conditions all the other 

 whipcord Veronicas — V. lycopodioides, V. hectori, &c. — will 

 equally rapidly produce reversion leaves. Nor is it always 

 necessary to give such moist treatment as the above. Eooted 

 cuttings placed in a fairly sheltered spot in a flower border 

 will revert so far as the young growth is concerned, though 

 such reversion will be soon succeeded by normal growth. In 

 my shade-house this spring both V. teiragona and Ozothamnus 

 microphyllus are rapidly developing true leaves. Other plants 

 with adaptations against drought of other kinds will also 

 under similar treatment change their leaf-form. Olearia 

 cymbifolia, planted in the open border, will often produce a 

 growth of flat leaves, instead of the normal leaf with strongly 

 revolute margins. This change seems to have a tendency 

 to remain more or less permanent, a plant growing on the 

 extreme summit of a rockery in my garden having leaves not 

 nearly so revolute as the type. Another plant in the shade- 

 house for nearly twelve months has now every leaf flat. On 

 the other hand, plants growing in cultivation in a dry part of 

 the garden show no change. The similar behaviour of Car- 

 michaelia (any leafless species), Baoulia eximia, and B. bryoides 

 could also be cited. 



* Pflanzenbiologische Schilderungen Erster Teil, Marburg, 1889, 

 pp. 19, 20. 



t Regarding Brown's work, see also Cockayne (loc. cit., p. 360). 



