290 
THE LEAF 
others, as clematis, the petioles are used to help the plant in 
climbing. In the pea and grape, leaves have become modi¬ 
fied into tendrils which 
are used in helping the 
plant to climb. (See Fig¬ 
ure 270.) Still others 
have their leaves modi¬ 
fied to thorns for protec¬ 
tion, as in the thorny 
locust. 
255. Leafless Plants. 
— In plants like the cac¬ 
tus, already mentioned, 
the work usually done by 
leaves is performed by 
the stem. Asparagus is 
a, plant in which a much- 
branched stem serves as 
leaves, the true leaves 
being almost invisible 
scales. Another example 
is the plant commonly 
called smilax, in which 
the branches very closely 
resemble leaves. 
Other plants which 
have scales instead of 
leaves are dodder and 
Indian pipe, both of 
Figure 268.-Indian P.pe. which use food all ' Cad > r 
A saprophytic flowering plant. prepared. 
256. The Movement of 
Leaves. — Most movements of leaves are/due to unequal 
growth caused by the light being brighter on one side than 
on the other. Some leaves on this account “ follow the 
