120 BRITISH PLANTS 
trailing stems and small leaves. The long internodes 
are the direct result of weak light ; the small leaves are 
due to malnutrition, resulting from the impoverishment — 
of the chlorophyll through lack of light. In extreme 
eases the chlorophyll becomes yellow or etiolated, and 
ceases to make starch altogether ; the plant then starves 
to death. 
Fic. 38.—EvERLASTING PEA witH Lerar-TENDRILS AND WINGED STEM. 
(REDUCED.) 
The evolution of the climbing habit may be traced in 
several of our common British plants. The woody night- 
shade shows how an ordinary plant may become a twiner. 
The common fumitory (fumaria officinalis), and its near 
relation, the climbing corydal (Corydalis claviculata), give 
us an idea of one method by which the tendril may be 
evolved. These two plants are occasional climbers, with 
large, much-dissected leaves. The leaflets are small, and 
the whole leaf appears to be more or less sensitive, so 
