20 
MODIFYING INFLUENCES—SALINE WINDS. 
same species individual trees and groups of trees may differ m hardiness If we 
search for the cause of this difference, we shall almost certainly find it m the 
original geographicanocation of the parent trees m Australia. L or, as already 
explained, a species with a far extended natural range may by long association 
have become adapted to mild conditions in one part of its habitat and to hard con¬ 
ditions in another part. Frost resistance is affected by the period of the year at 
which the low temperature occurs; for, as every farmer knows, a mild trost m 
summer may inflict more injury upon vegetation than a much more severe one m 
winter. In tree culture, moreover, we are entitled to count on the modifying 
influence of shelter. Trees help trees; and a judicious use of hardy species as 
protectors and nurses will often make the rearing of tender ones easy where other¬ 
wise it would he impossible. Even when the trees in a plantation are all of 
one species and all tender they will, if there are plenty of them, mutually befriend 
each other, and soften the effect of either a severe frost or a harsh wind. 
The modifying influences just mentioned are all such as we can easily under¬ 
stand; but from time to time there come in other influences the nature of which 
will not he so obvious. When so many trees were seriously injured or killed right 
out by frost in Canterbury in 1899 and again in 1903, it was found that the 
eucalypts on the higher ground where they had been weakened by pievious 
drought suffered very severely, while others of the same species along the rrveis 
and water-races almost escaped injury. Whether vapour in the air along the 
water channels, movement of the air itself, percolation of warmer watei 
about the roots, or the greater vitality of the trees made the difference, we 
do not know. The frosts were of phenomenal severity and trees of other genera 
besides Eucalyptus also suffered. Results were noted by competent observers in 
several localities; but no attempt appears to have made at the time to explain why 
nature favoured the trees that already enjoyed the advantage of being near water. 
But though the frost-resistance of a species cannot be always stated in 
exclusive terms of the thermometer, there is an accumulating mass of experience 
to show that competent thermal records are indispensable for safe and profitable 
planting. 
SALINE WINDS. 
Next to a temperature above or below its capacity the worst enemy to a 
eucalypt in this country is a strong saline wind such as often blows from sea to land 
along our exposed coast lines. There are many species that simply cannot endure 
the full blast of such a wind. The effect upon the trees is similar to that of frost. 
They lose their tender growing foliage and die back. This happens repeatedly 
until the trees are either permanently dwarfed or killed to the root. Other species 
are moderately resistant, and when planted in wide belts or blocks can maintain 
fair vigour and growth in exposed situations. Strong sea winds are injurious to 
many other genera besides Eucalyptus; and generally the sea-side farmer will do 
well to protect his plantations with screens of the hardiest conifers. Araucaria 
excelsa (North Island only), Cupressus macrocar pa, Finns radiata ( syn . F. 
insignis), and Finns muric at a have proved themselves eminently suitable for such 
purposes. The very tender eucalypts may need protection at a distance 
of ten to fifteen miles from an open coast. Reasoning theoretically, we 
