104 TRANSACTIONS OF THE [SEss. Lxxv. 
ON THE PEOPLING BY PLANTS OF THE SUBALPINE RIVER- 
BED OF THE RAKAIA (SOUTHERN ALPS OF NEW 
ZEALAND). By L. Cockayne, Ph.D., F.L.S. (Plates 
TX Xs, and, XE) 
CONTENTS. 
PAGE 
1, GENERAL J : ; : . : 3 , ‘ ‘ . 104 
2, PHYSIOGRAPHY ‘ , f ; , ; : 3 i OG 
3. ECOLOGICAL ConpiTIons . - . . : ; : ~ sB9 
(a) CLIMATIC. ; , ; : : : : : . 109 
(b) EpAPHIC : ; 3 : ; : ‘ P : oer gli: 
4. GROWTH-FORMS ’ ; : ; , : ; ; : apenas 
(a) GENERAL. ; é : He pays 
(b) SYNOPSIS OF SPECIES AND GROWTH-FORMS : . s Balls 
(c) THE RAOULIA-FORM : , ‘ 3 és : Saba y L) 
5. THE PEOPLING OF THE RIVER- BED F 2 , y ty PEED 
(a) GENERAL . ; ; ee Ay 
(6) THE UNSTABLE BED (EPILOBIUM AssocIATIon) ; 3 a 
(c) STABLE RIVER-BED , : P ; : : ; 74120 
a. RAOULIA ASSOCIATION . ; ; F y : ae eh20 
i STEPPE : , : . k ; ; PTS. 
ScruB ; F : vie pl PA 
(d) Astaetice oF THE RIVER- BED ASSOCIATIONS : z a ae 
1. GENERAL. 
The relation between the evolution of a land-form and 
its plant-covering is a matter of high phyto-geographical 
interest, but one extremely difficult to estimate in the 
majority of cases, although it seems evident that such a 
relation must exist. The difficulty arises from the fact 
that, while geological changes are extremely slow, those 
of vegetation are comparatively rapid. These latter, too, 
depend not merely on the topography, but also on climate, 
on the plants themselves, and on those changes which occur 
so frequently in the soil, independently of any surface- 
change. There are cases, however, where the evolution of 
a land-form may be so rapid as to be watched, as also its 
synchronous occupation by plants, while the plant-forma- 
tions themselves may be so distinct, each for its own 
particular land-form, as to be easily noticeable. The best 
known case of this kind is afforded by the land-forms and 
the plant-associations of a dune-area.! 
' For a description of those of New Zealand see Cockayne, L., Report 
on the Sand Dunes of New Zealand, Wellington, 1909. 
