The Vegetation of Western Australia. 
xliii. 
Floristically, however, the formation is not richly endowed. The herb- 
aceous plants are poorly represented, and there are but a few lianes, mostly 
Hardenbergia, Kennedya, and Clematis. It has been stated previously that 
the lateritic formations are usually poor in species, and this rule holds good 
for the jarrah forest. The forest attains its best development in the vicinity 
of tiie Blackwood River, where the undergrowth, due to a heavier canopy, 
becomes less dense, and Pteridium becomes important in the lighter soils. 
The jarrah and its competitive trees are rough barked, a (iharacteristic which 
is unusual amongst the trees of southern Western Australia. 
(ii) The Karri Forest. 
Tlie karri forest stands in sharp contrast to the jarrali forest by reason 
of its larger trees, the mesophytic undergrowth, and the better development 
of an under-storey of trees, in which Casuarina decussata, Agonis flexuosa, 
Banksia, and Hakea take a prominent place. The shrubby undergrowth is 
higher, Acacia pentadenia one of the Bipinnatae, with large-leaved shrubs 
such as Trymalium, Chorliaena, Hovea elliptica, and Albizzia, and in the open 
spaces, areas of tall Pteridium, often exceeding two or three metres in height. 
The sclerophyllous plants of the jarrah forest have larger, less sclerophyllous 
leaves, and the smaller shrubs and herbs are of straggling widely-branched 
habit. Indeed, the wide branching and interlocking of branches is at once in 
marked contrast to the shrubs of other formations, as well as the tendency 
for species to become ombrophytes. The principal shade is, however, not 
<lue to the density of the canopy provided by the principal trees, for although 
these, the karri {Eucalyptus diversicolor), tingle trees {E. Jacksoni and E. 
Guilfoylei), and Marri {Eucalyptus calophylla) are precisely those that have 
the widest and most horizontal branching habit of all the south-western species 
of the genus, they do not give much shade. The shade is provided by the 
under-storey of smaller trees, especially Casuarina decussata and Banksia 
grandis, or the other species of Banksia. The true ombrophytes are those 
species w'hich live on the forest floor, such as Dampiera hederacea, the species 
of Boronia, Tremandra, and Opercularia. 
Unlike the jarrah forest, the karri forest secures its edaphic requirement 
in the soils derived from the granitoid or gneissic rocks which more or less 
determine its occurrence in its general area of distribution, and account for 
outlying areas on the Porongorup Range, and near Mount Manypeak. The 
karri forest occurs bet-ween Denmark and the Blackwood River estuary, 
where the rainfall during the six driest months exceeds 200 mm. The density 
of the vegetation, both amongst the arborescent or fruticose species, together 
with the occasional occurrences of epiphytic ferns, gives to the karri forest a 
physiognomy not possessed by any other plant formation in Western Aus- 
tralia except the riverain forest of the Kimberley Division. It is really a type 
of temperate rain forest. 
(iii) The Tuort Forest. 
The tuart forest is a type of savannah forest in which the trees of the 
tuart {Eucalyptus gomphocephala) attaining a height of 40 metres, dominate 
tlie forest in almost pure stands, being only rarely associated with such 
s]iecies as E. calophylla and E. cornuta. It is edapliically confined to the 
littoral limestone of the western coastal plain, the range of the species ex- 
tending from near the Hill River to the Sabina River near Busselton. It is 
only in the southern jiart of its range, w'-here the summer (November-April) 
rainfall excieeds 125 mm. that it attains to the proportions of a forest in its 
species. Here it is a true savannah formation, with an understorey of 
