62 THE FLOWERING PLANT. 
and separated by a constriction from the lamina, which is com- 
posed of two oval halves, the margins of which are provided with 
bristles, while the upper surface of each bears about three slender 
, highly sensitive hairs. In one of the 
pitcher - plants, Nepenthes (fig. 27), 
species of which occur in Madagascar, 
Ceylon, and the Hast Indies, the mid- 
rib of the simple leaf extends beyond 
the apex of the lamina as a tendril, 
which terminates in a lidded pitcher 
resembling a hot-water jug in shape. 
The bladder-wort (Utricularia) is an 
aquatic herb, sparsely distributed in 
British ponds and ditches. Its leaves 
are pinnately parted into numerous 
narrow lobes, some of which bear 
small-stalked bladder-like structures, 
each of which possesses an inwardly- 
opening valve-like aperture. 
The texture of the lamina may be either herbaceous, leathery, 
or succulent. he first characterizes most of our common leaves, 
which are deciduous, t.e., shed annually (p. 43). Leathery leaves, 
capable of greater endurance, are found in evergreens, which 
owe their name to the fact that the foliage is-shed gradually, 
so that the branches are never bare. Succulent leaves, such 
as those of the aloe, are especially characteristic of arid climates 
(cf. p. 27): 
The colour of the lamina is not uniform. Not to mention 
spotted, mottled, and variegated leaves, it usually happens that 
the upper side is of a darker green than the lower. This is 
principally due, as we shall see, to the way in which the internal 
green tissue is arranged. But the colour is also dependent on 
the nature of the surface. This may be glabrous, especially in 
evergreens, or more or less hairy, and in the latter case it is usual 
for the hairs to be more numerous on the under side, giving this 
a whitish hue. Silverweed (Potentilla anserina) is a beautiful 
example, and the same thing is seen to a less extent in wallflower, 
buttercup, &c. Some leaves are of a bluish-green colour, and 
this may be due to the presence of wax, as in the garden poppy. 
Glandular hairs are frequently found on the lamina, and these 
very often secrete a fragrant oil, as in lavender, where short 
glandular hairs are mixed with larger branched non-glandular 
ones. The perfume patchouli is obtained from a similar source, 
and the odour of sweet-briar is also due to such hairs. Stinging 
hairs may be present on the lamina (petiole and stem) as in the 
FIG. 27.—Pitcher of Nepenthes. 
