LEAVES 31 
into very numerous small leaflets, sometimes very small, 
which stretch in pairs along the leaf branches. When a 
drought begins, some pairs of leaflets fold 
together, slightly reducing the surface ex- 
posure. If the drought continues, more 
Fic. 27.—Leaf of sensitive plant in two conditions: A, fully expanded, with the 
four main branches and numerous leaflets well spread; B, after a shock of some 
kind, the leaflets being thrown together forward and upward, the four branches 
having been moved toward each other, and the main petiole having dropped 
sharply downward.—After DucHARTRE. 
leaflets fold together, then still others, until finally all 
the leaflets may be folded together, and the leaves them- 
Fic, 28.—The day (A)-and night (B) positions of the leaves of a clover-like plant. 
—After STRASBURGER. 
selves may bend against the stem. In this way the ex- 
posed surface may be regulated according to the need. 
