124 PLANT STRUCTURES 
plished by means of the formation of a transverse 
layer of corky tissue across the base of the leaf-stalk, 
combined with a weakening of the layer of cells im- 
mediately above. Prior to the perfecting of these 
arrangements for dropping the leaf, all the useful 
materials in it are withdrawn down the stem, so that 
only an empty skeleton is shed; the scar that remains 
is not an open wound, but is well protected by the 
corky layer before mentioned. 
Stipules and bracts need not delay us in this 
sketchy survey of plant organs. They are leaves, 
generally of rather small size, placed, the former one 
on either side of the point where a leaf-stalk emerges 
from the stem, the latter singly below a flower; they 
are present in some plants, absent from others. They 
function in the same way as ordinary leaves, and in 
the earlier stages of growth are of use protectively. 
Occasionally the stipules exceed or even replace the 
leaves, as in the native Lathyrus Aphaca, where the 
leaf is reduced to a tendril, and the pairs of broad 
“leaves” are really the stipules. The bracts, in their 
turn, sometimes take on the “advertisement” function 
of the petals, as we have already seen (p. 87) in the 
case of certain Euphorbias. 
The leaves of water plants offer several points of 
interest. Where they are entirely submerged, and, 
protected against the drying influence of wind and 
sun, they are of filmy texture. Broad blades are 
seldom met with, the leaves being usually either finely 
dissected or strap-shaped. The floating leaf, on the 
contrary, as already described in the Water Lily, is 
strongly built up, to withstand wave action and rain; 
it is usually broad and entire, which simplifies the 
