THE SENSITIVE PLANT 133 
Appearance of the sensitive plant. The leaves of 
the sensitive plant are rather large. A leaf is: com- 
posed of a large number of leaflets (pinne) arranged 
in pairs along four different axes, which are joined to 
a stalk (the petiole of the leaf) somewhat as the toes of 
a bird are joined at the foot. <A single leaf is shown 
in Fig. 160 attached to the shoot. Imagine 
a branched shoot with a number of these 
leaves and you will know how the sensitive 
plant looks. 
Movement of the leaves of the sensitive 
plant. When you wish to test the plant, it 
should be on a bright day, though the plant 
will work on a cloudy day also if it is not 
too dark. It must be left undisturbed and 
quiet for some time before using. We must 

be careful not to touch or jar it until we 
are ready. Fig. 161, Move- 
ment of the 
Now, with a pair of forceps, or with the Pehse stra, 
fingers, pinch one of the terminal leaflets. ?™°™s°"® 
Instantly the terminal pair clasp or fold together above 
the axis. Then the second pair do the same, and the 
third and fourth pairs follow quite regularly. This 
movement continues, successive pairs closing up until 
all on the axis are closed. Then the last pairs on the 
other three axes fold together, and successive pairs on 
these close up until all are closed. By this time, 
