LEAVES 35 
light, but they produce leaves reduced in size and without 
green tissue. Often these scales seem to be merely useless 
relics (lig. 64); but sometimes they are used for food 
storage, as in lily bulbs, onions, ete., which are mostly made 
up of fleshy scales (Fig. 65). 
In the scaly buds, so common on shrubs and trees, the 
overlapping scales are clearly protective structures, and to 
this end are generally firm and resistant, often coated with 
resin, the inner ones being frequently clothed with woolly 
hairs. 
(2) Tendrils.—The whole leaf or some of its branches 
may develop as tendrils, the latter case being illustrated by 
the sweet pea (Fig. 32). Ten- 
drils are sensitive to contact 
and aid in climbing. Some- 
times leaves act as tendrils 
without any modification of the 
blade, the petiole being sensitive 
to contact and encircling sup- 
ports like a tendril, as in the 
garden nasturtium. 
(3) Thorns.—Leaves develop- 
ing as thorns may be observed 
in the barberry (Fig. 33). In the 
common locust, acacia, ete., only 
the stipules develop as thorns. 
Both tendrils and thorns are 
also developed as stem struc- 
tures, being modified branches. 
(4) Leaves of pitcher-plants.— Fic. 32.—Pinnately compound 
ie leaf of garden pea, whose ter- 
In these plants the leaves form Hibs Gautioaies alewdlawed 
tubes or urns of various forms, as tendrils. — After Srras- 
‘ . BURGER. 
which contain water; and to these 
insects are attracted and drowned. The common pitcher- 
plant of the northern States, a Sarracenia, is a well-known 
