SrEMUiT, C'ocKAYXK, ]j.\iX(;. — Mount Arroirsniifh Dixtnct. 353 



the nionotony of the tussock is relieved by green clumps of trees. These 

 consist of Gaya ribifoUa, a low tree 6 m. tall, more or less. A few ferns 

 may grow beneath the trees — e.g., Blechnmn penna marina, Hypolepis 

 millefolium, Pohjstichwn vestitmn, and on the outskirts a few divaricating 

 slirubs. 



The presence of Gaya ribifolia is a sign of steppe climate, since a forest 

 climate at once replaces it with the closely allied G. Lyallii. Both are 

 strictly deciduous, but differ ecologically in their leaves, those of G. ribi- 

 folia, covered with hairs, being more xerophytic than the almost glabrous 

 adult leaves of G. Lyallii. Both species pass through a somewhat similar 

 persistent juvenile stage of development. 



(/.) Nothofagus cliff ortioides Forest. 



.V. cliff ortioides forest may be considered the climax association of the 

 subalpine-steppe climate. It occurs very sparingly in the Arrowsmith dis- 

 trict, and is confined to a few gullies, or there may be merely a few trees, 

 scattered or in clumps on the banks of streams. 



i\". cliffortioidcs is a low canopy tree with a close head of small stiff 

 leaves. The branching is distichous, and the foliage consequently lies in 

 layers. The trees are probably not very, long-lived, and fall before the 

 wind as they decay, their place being taken by a close growth of saplings, 

 which, as seedlings, formed most of the undergrowth. 



The following were noted as forming the undergrowth : Blechnmn fenna 

 marina (creeping fern), B. capense tufted fern), Hypolepis millefolium 

 (summer-green creeping fern), Podocarpus nivalis (prostrate rooting shrub), 

 Aristotelia fruticosa, Coprosma propinqua, C. parviflora (divaricating-shrub 

 form), Griselinia littoralis (bushy shrub). Fuchsia excorticata (small deci- 

 duous tree), JJrtica incisa (erect herb). Doubtless a number of other 

 species are present, but at the best this association has few members. 

 Elytranihe flavida (hemi-parasite) grows on the Nothofagus. 



At one period, as also in Central Otago and elsewhere, as already noted 

 by Speight, where now a steppe climate prevails there must have been 

 extensive totara forests, for remains of trees lying on the ground have been 

 frequently noted, as, for example, in the Cameron Valley according to Mr. 

 L. Wood (see also Monro, 1869 ; Buchanan, 1869). 



If such a forest existed, and occupied a wide area in the eastern sub- 

 alpine and montane belts of the South Island, it seems almost impossible 

 that it could have been altogether destroyed by fire, as popular and even 

 scientific opinion has declared (sec Monro, 1869 ; Buchanan, 1869). The 

 only feasible explanation, then, is that put forth by Speight— that the 

 climate not very long ago, geologically speaking, was more mesophytic 

 than at the present time. If the Rakaia Valley be alone considered, it is 

 almost certain an advance of the average western rain-line a few miles to 

 the east would be followed by an advance of the present totara forest, and, 

 although extending no further, it would persist for a long time after the 

 climate had become xerophytic. On the other hand, a rainfall similar to 

 that of the western Rakaia has only brought Nothofagus cUffortioides forest 

 in the western Waimakariri district. 



(g.) Lake, Swamp, Bog, &c. 



The above series of associations are dealt with in this place because 

 the climax association of a lake captured by vegetation is steppe, though 



12— Trans. 



