350 Transactions. 



are 60 cm. tall A detailed account of the ecological history of a western 

 subalpine river-bed by Cockayne will shortly appear in the "' Transactions 

 of the Botanical Society of Edinbiu'gh." so little more need be said here. 



Eastern river-bed vegetation commences with the same Raoulia species 

 as eastern fan, and the procession of events is very similar, while it is obvious 

 that the tussock steppe of a river-terrace summit has gone through the same 

 changes as are happening on river-bed at the present time. 



The old bed of the Ashburton near Hakatere is occupied by an extremely 

 xeroph^'tic subassociation. which would repay detailed investigation. Tus- 

 socks are few in number and far apart. The vegetation is quite open. The 

 substratum is flat, very stony, and with but little fine soil. The xerophytic 

 whitish moss Bacromitrium Januqinosmn is abundant, growing between the 

 stones. There are many broad patches of the narrow erect flat green leafless 

 stems of Cnnnichaelia uniflora and C. Emisii. Low silvery circular cushions 

 of Eaoulia lutescens are abundant. Discaria toumatou and Helichrysum dc- 

 pressum. no longer erect, are flattened to the groimd. Coprosma Petriei 

 (close turf-making subshrub with stout creeping stems and very small linear- 

 oblong coriaceous leaves), Wahhnbergia saxicola (mat-forming, creeping, and 

 rooting herb with small thick coriaceous leaves in open rosettes), Acaena 

 inermis (mat-forming, creeping, and rooting subshrub with wiry stems and 

 rather thin glaucous or reddish pinnate leaves in open rosettes), some green 

 cushions of Eaoulia Haastii. and a few flat or raised silvery round patches of 

 /?. austraJis. There are doubtless other species present. The subassociation 

 occupies a wide area. It probably owes its structure and character not 

 only to the edaphic conditions, but to the wind-swept habitat. An ephar- 

 monically similar subassociation occurs on the most stony gromid of the 

 Canterbury Plain, but the Carmichaelia is C. nana and the principal Raoulia 

 is R. Monroi. 



(d.) Tussock Steppe. 

 * General. 



Montane and subalpine tussock steppe is merely a continuation of the 

 same formation of the lowlands, and extends over much of the mountain 

 area on the east of the Southern Alps, and has a fairly uniform floristic 

 composition throughout. Tussock steppe is economically far and away the 

 most important indigenous plant formation of the Dominion, and a thorough 

 knowledge of its ecology is distinctly a matter of national importance. This 

 statement is emphasized by the fact that overstocking and burning have 

 so modified the original tussock steppe in various parts of the South Island 

 that the value as pasture land is gone, a true desert having replaced the 

 original grass land (see Cockayne, A. H., 1910). 



** GrowtJi-fornis. 



There are doubtless considerably more species in the association thau 

 given in our list, but a consideration of those contained therein should be 

 quite sufficient to give a clear idea as to the gro\\i:h-forms and their relative 

 abundance. 



. The number of species noted is 103, of which 15 are shrubs, 12 suhshrubs. 

 and 76 herbs. 



The shrubs are : Evergreen, lU ; deciduous, 2 : and leafless, 3. The 

 following groTAi:h-forms are represented : The creeping and rooting, 9, of 

 which 2 are the flat-stemmed leafless ; the prostrate non-rooting, 2 ; the di- 

 varicating, 2, of which 1 is spiny ; the bushy, 1 ; the tall flat-stemmed leaf- 

 less, 1. 



