96 
examples. In many of our xerophytes, too, the epidermal cells 
are ot considerable size and contain an appreciable reserve ot 
water. This is particularly noticeable in the “ice plant./’ 1 * 3 
Chief plan! activity, however., has been directed towards 
minimising transpiration, boss ol' water is a source ot grave 
danger to most ot our bush plants. It I he rate ot such loss exceeds 
that at which absorption proceeds, the plant is forced to draw on 
its water reserves. Should these become depleted, growing lips 
of roots and shoots lose power ot growth, drooping commences 
and slid further desiccation results in permanent injury or death. 
IUi( transpiration is a necessary danger. In plant nutrition, con- 
structive metabolism demands at least seven soil constituents. 
These can he obtained only in solution by the absorptive system 
of the plant. The continuous supply of these soil constituents is 
dependent, then, on the steady inflow of soil water. Since the 
water-liolding capacity of any plant is limited, it follows that the 
uninterrupted entry of dissolved minerals is dependent on provi- 
sion being made for the escape of water from the plant surface. 
Water loss, therefore, is necessary. In. humid climates, where 
evaporation is exceedingly slow, certain plants (Tropaeolum majus 
and Fuchsia) exhibit structural modifications which allow the 
exudation of water from definitely placed pores. In our dry 
season, however, hot dry air, renewed by almost constant winds, 
accelerates the rate of evaporation to such an extent that even the 
hardiest of our introduced garden plants needs the constant care 
and protection of the gardener. 
Normally, transpiration is not permitted to take place over 
the whole area of the plant. A waterproof cuticle restricts it to 
Hie stomata on the green portions, and in the corky regions lenticels 
•ire provided. To the lenticels ot our plants I have paid but little 
attention. They certainly art* not prominent features and prob- 
ably are poorly developed. Moreover, i( is to the neighbourhood 
of green surfaces that the transpiration current, brings the 
materials required in the metabolism following on phot osyntlietic 
activity. Stomata arc most numerous on leaf surfaces and there- 
fore it is to the leaves of xerophytes that we look for the chic I 
evidences of modification. 
1 have selected at random the leaves of a few ol our plants, 
rind m study of stained sections shows how their anatomy specially 
enables them to guard against excessive loss ot water vapour. 
1. Banksia. attenuafca. 
'Plate XV., Pig. 1, shows the typically bifacial structure ex- 
hibited by a transverse section of a leaf of this plant. Stomata 
3. \r. Crysfcallimiin. 
