64 SOUTH AFRICAN BOTANY 
34. Kind of Leaves.—Leaves may be divided accord- 
ing to their functions into four classes :— 
(1) Fohage leaves ; 
(2) Scale leaves ; 
(3) Bracts ; 
(4) Floral leaves. 
Foniacz LEAVES are the ordinary green leaves of the 
plant. Their chief work is to nourish the plant. This 
is performed by means of the green pigment chlorophyll 
present. They also possess numerous small holes in 
the epidermis called Stomata, through which respiration 
and transpiration can take place. Some plants produce 
two forms of foliage leaves, a phenomenon known as 
HETEROPHYLLY, or HETEROMORPHY. For example, the 
Eucalyptus globulus (Blue Gum) bears sessile oval leaves 
when young and sickle-shaped stalked leaves when older. 
The Water Crowfoot (Ranunculus aquatilis) bears two 
kinds of foliage leaves: (a) submerged leaves which are 
finely divided, and (0) floating leaves which are lobed. 
Scale Leaves are small brown sessile leaves, and are 
usually reduced forms of foliage leaves, as in the Oak. 
Their function is chiefly protective. They are found 
chiefly as Bup ScaLzs, small, brown, hard and thick 
leaves which protect the winter buds from cold in 
winter and spring. The scale leaves of the Horse- 
chestnut are really enlarged leaf bases, for the inner 
scales often possess rudimentary leaf-blades. The scale 
leaves of the Bird Cherry are modified stipules. 
Rhizomes, bulbs, and tubers always possess scale 
leaves, sometimes brown (e.g. onion), usually colourless 
and much reduced. 
