THE LIVING CELL 37 
secondary leaflets, after a latent period of less than 14 second, the 
leaflet stimulated rises and its partner almost at the same time. 
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=| YES. 
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B 
Fic. 18.—Leaves of Mimosa pudica, A, normal position; B, after stimulation. 
p, pulvinus or leaf cushion at base of petiole. Note the compound leaf consists of a 
long petiole ending in a blade of 4 leaflets, each of which possesses a secondary 
petiole with a pulvinus at its base, and a midrib which bears a large number of 
small secondary leaflets. A stimulus applied to the large pulvinus at the base of 
the main petiole will cause the latter to fall and the secondary leaflets to become 
erect with the upper surfaces of each pair of opposite leaflets against each other 
(B). (After Pfeffer.) 
The stimulus is then carried down the midrib, the pairs of 
secondary leaflets closing in order; in 9 seconds all the secondary 
leaflets have closed, the midribs converge, followed in 3 seconds 
