S3 
quite smooth all round, presenting to the air the least possible 
area ot surface, and ending most frequently in a sharp point. • 
It is interesting to note how the stems of trees and other 
plants are protected from injurious external influences. In a 
visit to the North-West I was struck with the fact that the few 
trees seen had their trunks and branches provided either with a 
rough, thick corky bark or had them smooth and quite white 
as if painted with a cooling composition such as that applied to 
the roofs of houses. In either case it evidently serves as a 
protection from the excessive sunshine and heat of the region. 
The heat of the sun and air is probably the cause of the develop- 
ment of the thick protective cuticle, like that on the palm of the 
village blacksmith, and the white stems reflect the light and heat 
of the sun, so that the interior of the stems will not suffer injury. 
When the moisture in the soil is not pure water, but contains 
particular substances dissolved in it, such as salt, many plants 
would be killed or injured if planted there, while others, like 
saltbushes, would grow and thrive. The saltbushes may grow 
well in an ordinary soil, so that a distinctly brackish condition is 
not indispensable to them ; but they have a tolerance or affinity 
for salt, and may extract more of it from an ordinary soil than 
other plants do, and store it up in their tissues. They thrive 
better in a moderate degree of brackishness, however, and their 
roots, when not in active growth, might suffer no injury from a 
somewhat concentrated solution, of salt, as those of other plants 
would. 
The subject of the adaptation of plants to their surroundings 
maybe said to be co-extensive with the Vegetable Kingdom, and 
we may go on speaking of examples of their ways and means of 
doing so indefinitely ; but it would be advantageous to consider 
some of the means by which the economically important family 
of Grasses maintain their position under trying conditions. In 
some grasses — for example, Sesleria tenuifolia, a South European 
species — a remarkable intricately-woven tunic is provided for the 
covering and protection of the lower parts of the stalks. The 
sheaths of the lower leaves — the part of the leaf embracing the 
stem — are composed of longitudinal and crossing zigzag fibres 
so woven together as to form an intricate network in the tissue 
of that part of the leaf. When the upper part of the leaf withers 
and drops away in dry weather this fibrous net remains as a pro- 
tective clothing for the stem of the grass during the trying period 
between summer and the following spring. Instead of having a 
woven fibrous tunic the base of the leaf sheath may be more 
straw-like in its nature, as in some of our native grasses : in 
drought, however, either texture is calculated to protect the plant, 
to absorb moisture when the chance occurs, and to retain it for a 
longer or shorter time during intermediate dry periods. 
In Australia and South Africa another form of protective 
