DEVELOPMENT AND DISTRIBUTION OF THE LEGUMINOSZ. 369 
Australia, while, on the other hand, the Hucalypts, the 
phyllodineous Acacias and other endemic plants havealmost 
the whole of Australia in which to develop. Thus the 
luxuriant forms have but insignificant opportunities of 
developing fresh species. 
From these considerations it would appear that the 
luxuriant types are much the older, while the xerophytes 
are by far the younger, forms in Australia.* This illus- 
trates, in a measure, a few of the principles of Geographi- 
cal Distribution, the main consideration being that all 
principles should be coordinated without clashing, thus 
excluding any hasty generalisation. 
Another principle governing the distribution of plants is 
that occasioned by the combined influence of soil and 
climate. Cambage has done pioneer work in this connec- 
tion in Hastern Australia. If this continent should be 
converted rapidly into an area of heavy and continued 
precipitation, and if the present poor sandy soils should be 
replaced by heavy ones, then the great bulk of the endemic 
vegetation of Australia would perish hopelessly. On the 
other hand, if the areas of heavy precipitation now sup- 
porting luxuriant vegetation in Australia should be supplied 
with a rainfall of less than 20 inches a year, and falling 
mostly in one season, then the types at present luxuriant 
would in turn vanish and the endemic genera would reign 
supreme. 
It might be interesting also to enquire how Hdwardsia, 
Kugenia, Myrtus and Leptospermum, could occur in New 
Zealand, while neither Acacia, Cassia, Melaleuca, Dalber- 
gia nor Hrythrina have been collected within that area. 
+ Since this report was written Mr. R. H. Cambage has drawn my 
attention to an article by Dr. Domin (31), in which the separation of 
Australia from Asia is supposed to have taken place at an early period, 
resulting in a great number of endemic species being developed in 
Australia. 
X—November 4, 1914. 
