300 Transactions. — Botany. 



temporary adaptations, have stayed, and in the course of many 

 generations have become specially differentiated for the rock 

 life. Others, again, belonging naturally to xerophytic stations, 

 may have been driven on to rocks by certain aggressive plants, 

 which have ousted them from their original position. The 

 study of such matters as this latter is, with regard to New 

 Zealand plants, in its infancy, and little can be said of any 

 scientific value. Chatham Island, however, furnishes one 

 very interesting case where a plant once very abundant is 

 almost driven from its principal stations, and will before 

 many years be found only in two places of the most opposite 

 character — viz., rocks and margins of lakes. From what has 

 gone before it may readily be guessed that I allude to Phor- 

 miuvi tenax. How its destruction has come about and how 

 it has settled in its new quarters will be explained in another 

 section. I need only say here that, although in this case 

 human influence has been the chief agent, how can one tell 

 that such also has not been a determining factor in bringing 

 about certain local distributions of plants in the Old World? 

 Also, it is well known that without human agency of any 

 kind one plant can replace another. 



The cone-like volcanic hills have in some instances rockv 

 summits. On such bare volcanic rock grow the orchid Earina 

 autwnnalis and the very thick-leaved fern Polypodium serpens, 

 both of which are also epiphytes of the forest. The decay of 

 the earlier lichens and mosses paves the way for this later 

 vegetation. In such vegetable matter on the perpendicular 

 side of Maunganui Hill grows a short-leaved form of Asplenium 

 Jiaccidum in company with Polypodmm serpens. The roots of 

 the Asplenium are densely covered with hairs, and form a mat 

 spread out for a distance of 15 cm. No station much more dry 

 can be conceived than the face of such a perpendicular vol- 

 canic rock. Of course, in wet weather the decayed vegetable 

 matter will absorb water readily, but at the time of examina- 

 tion it was as dry as dust, and certainly the plants would not 

 be able to absorb any moisture from it whatsoever. Under 

 such circumstances these plants must depend entirely upon 

 the water stored up in their thick leaves. On the summit of 

 another rock near by I saw a number of both young and old 

 forest trees, the latter much stunted, growing in peat, then 

 quite dry, of not more than 20 cm. depth. 



The Horns is the name given to a volcanic hill at the 

 south-west corner of the island, and which receives its name 

 from there being two rocky cones rising close to one another, 

 and much of the same height. On the steep rocky face of 

 the more easterly horn are growing Phormium tenax, Poly- 

 podium billardieri, Veronica sp. (neither V. dieffenbachii nor 

 V. chathamica), Muhlenbeckia. adpres^a, Linum monogynum 



