XXll 
Charles Austin Gardner. 
From this original stock, a type of Acacia has originated which is 
characterised by the production of phyllodes, the leaf being represented by the 
simple flattened leaf-like axis of the compound leaf. Its ontogeny may be 
observed in any species of this type, and transitions between the two may be 
observed in Acacm insolita, a species of the eastern borders of the jarrah 
forest, w^hich normally possesses both leaves and phyllodes. This large 
grou }5 (the Phyllodineae), numbering over 400 species, is, with the exception 
of a few Papuan and Pacific species, confined to Australia, the Western Aus- 
tralian species numbering over 300. They are found wdthin every formation 
throughout the country, assuming remarkable diversity in form and varying 
from complete aphylly to large leaf-like phyllodes. Their highly developed 
floral economy, and the adaptation of a leaf-stalk or even a stem fimctioning 
as a leaf, has enabled them to withstand extreme aridity of environment, 
and thus they have penetrated into the arid heart of the continent, developing 
an epharmony which leads to complete aphylly. 
While this epharmonic development is in most examples progressively 
manifested as w'e travel from w^etter to drier areas, there are w^hat appear 
to be retrograde divergences in some instances. For example. Acacia alata 
and A. cxtcnsa, both of w'hich inhabit wet or marshy spots in the south-western 
forests, exhibit an apparent morphological xerophily which is misleading, 
for histologically Acacia alata at least, is a mesophyte. It lives only under 
conditions of shade and moisture wfiiich are the ideal conditions under which 
the leafy Acaciae find their true environment ; the phyllodineous species, on 
the other hand, have attained to their highest development under arid con- 
ditions, or at least, seasonal droTight. Australia, and particularly Western 
Australia, is the richest in species of Acacia of any part of the earth, but the 
genus cannot be considered as belonging to any but a tropical element. 
What is true of Acacia is ajjparently also true of the rest of the Mimosaceae 
and the Caesalpiniaceae. In this connection it is interesting to consider the 
range of Albizzta, indigenous to tropical Asia, Africa, and Australia, fhe 
Western Australian representatives are confined to the trojiical north with 
the single exception of Albizzia distachya, confined to the south-w^est. Of 
the Caesalpiniaceae, both Petalostyles and Labichea are endemic in Australia, 
and are closely related to Cassia, from which they have probably been evolved ; 
Petalostyles remaining megathermic, while Labichea extends from Queensland 
to south-wustern Australia, but without a continuous distribution between 
the Murchison River and the Northern Territory. Cassia, on tlie other 
hand, which w'e must regard as a tropical element, has migrated far to the 
south, but has not extended into the wet south-wust, and its real liome in 
Australia in the savannah and the dry interior, where, by the provision of a 
dense indumentum of felt or hair, it has, with practically no structural modi- 
fication, iDenetrated to the desert. 
Space does not permit me to deal at any length with the third family of 
the Leguminosae — the Papilionaceae, and the family is so large, and of such 
cosmopolitan distribution, that it is difficult to trace with any exactness its 
possible migrations. It is w'orth remembering, however, that every tribe 
of this important family is represented in America, which country appears to 
be the main centre of distribution for the family. The Dalbergieae, Sophoreae, 
Hedysareae, Swartzieae, Galegeae, and Phaseoleae are all most richly de- 
veloped in America, five of them being found in Asia and Australia. Of the 
remaining five tribes, the Vicieae, Trifoleae, and Loteae arc more cosmo- 
politan in distribution, but mainly of northern development, while in the 
