16 
THE AUSTRALIAN CLIMATE. 
SECTION II. 
CLIMATIC ADAPTATION. 
A complete grouping of the species on a basis of ascertained affinity still 
remains to be worked out; but we need not therefore be deterred from research in 
other directions. The question upon which the grower of the trees most pressing y 
needs guidance is climatic adaptation; for if he knows everything else about a 
species but does not know its climatic range, he may easily waste his time and 
money in planting it. Nature has decreed that each species shall be at its best, 
or, as the scientific people say, at its optimum, in certain climatic conditions, and 
shall decline in vitality when and where those conditions greatly change 01 cease 
exist. For one species the range may be very restricted, for another very tar- 
reaching; but for all there are limits. And the general truth we have to accept is 
that a species of otherwise inferior merit at its best will often be more valua e 
than a species of otherwise superior merit at its worst. In transferring plan s 
from their natural habitat to another country we need competent knowledge of the 
climatic conditions that prevail in the original habitat as well as oi those that 
prevail in the country where the plants are to be cultivated as exotics. 
CLIMATIC CONDITIONS IN AUSTRALIA AND TASMANIA. 
The great continent of Australia and the island of Tasmania together present 
an immense range in latitude, in contour of the land, in mean annual temperature, 
and in maximum and minimum rainfall; and every geographical province in these 
countries has its eucalypts. Some of the species are restricted to tropical areas 
where a summer of continuous high temperature is followed by a frostless winter. 
Many are sub-tropical and have their home in regions where the contrast of con¬ 
ditions is between a torrid summer and a winter with mild frosts and cool breezes. 
Others grow to large dimensions where the summers are changeable and the 
winters cold. A few belong to the high mountains and may be found flourishing 
above the winter snowline. Many of the species require a moist, deep subsoil and 
a generous rainfall; others yield their most valuable crops on stony hills where 
moisture is less abundant; while there are some that can survive and grow to a 
useful size where the annual rainfall is less than 15 inches. Some of the well 
defined species have almost certainly been growing in successive generations for 
thousands of years where we now find them. Several species are found on both 
sides of Bass Strait, and have remained almost identical since Tasmania was 
separated from the mainland. Species common to Tasmania and the mainland, or 
to Victoria New South Wales and Queensland, find climatic compensation for 
themselves by growing nearer to sea level in southern parts of their habitat and at 
higher altitudes as they extend their range northwards. This, of course, is in 
accordance with a law of adaptation imposed generally upon plant life. But 
coincidently with this adjustment of altitude to latitude there has been operating 
