!xiv. 
Charles Austin Gardner. 
over a diameter of over tive metres. Fire destroys the aerial parts, and 
from the periphery a ring-like growtli ensues, or this may be broken up into 
a number of independent plants. 
The distribution of the grasses in Western Australia is interesting, sineo 
it shows that they fall mainly into tw'o thermal groups — a megathermic group 
of (>3 genera, representing mainly the Paniceae, Andropogoneae, and I'lra- 
grosteae, with a number of endemic genera, and a mesothermic group of 17 
genera, represented chiefly by the Festueeae, Aveneae, and Agrosteac, with 
but one endemic genus, Diplo 2 :>ogon. There are few genera which are common 
to both areas^ — Neurach^^e extends to the north, but is more proptu'ly to be 
considered of southern derivation ; Triodia, Eriachne, Eragrostis, and Sporo- 
bolus extend far to the south, but must be considered a northern element > 
The Sections Arundineae, Chlorideae, Zoiseae, and Arundinelleae are ox- 
clusively groups requiring a warm summer rainfall, and the Andropogoneae 
are characteristically of this element also. In the Stipeae, Aristida is mega- 
thermic, while Stipa, its southern counterpart, is mesothermic. Stipa and 
Aristida are common only to the eastern districts, the former being mainly 
south-western, the latter northern. 
It is imj)ortant to consider also the recpiirements and the development 
of the grass flora in south-western Australia. The grasses here are sometimes 
of a very restricted habitat. For example, Tetrarrhenn and Microlaena are 
confined to the forests and woodlands of the highei* winter rainfall areas ; 
iSporobolus, togetlier with Puccinellia, Ayuphibro^nus, Deyeuxia, Poa, Era- 
grostis, Lep>turus, PholiurtiSy and Dichelachne show a j^reference for loamy or 
swampy soils, wet at least in winter ; while Dantkonia, Neurachne, A)nj)hi- 
pogon, Diplopogon, and Stipa favour the sandy soils, and attain their 
greatest development in the southern regions whei’e the summer rainfall 
is higher than elsewhere. For example, Danthonia is not common on the 
west coast further north than Cingin, while it is fairly common along the 
southern littoral. Festuca finds a suitable environment both on the littoral 
dunes and the hard loam of the interior. 
Apart from the shade-loving or paludal species, the grasst's of the south- 
west appear to fa\'our the granitic soils, and prt'dominate in the savannah 
woodland which separates the sclerophyllous woodland from the forest. The\* 
are most abundant where the summer rainfall is higher than elsewhere (ex- 
cluding the forest area), and under its influence we occasionally find an inter- 
mixing of both northern and southern types, as at Jarramongup and C.'ool- 
gardie. 
In conclusion I must express my thanks to the Divisional Meteorologist, 
Mr, A. G. Akeroyd, for permission to publish rainfall and other meteorological 
statistics, also for kindly reviewing the chapter dealing with the climate ; to 
Professor E. de C. Clarke for assistance in the chapter on geology and soils ; 
and to Mr. F, M. Bennett for compiling some of the tables which ha\-e app(‘ared 
in the appendix. Finally, I am indebted to Dr. Gentilli of the University 
of Western Australia, for permission to use his statistics dealing with annual 
rainfall variability. 
