368 MODIFIED CIRCUMNUTATION. CHAP. VII. 



Apios tuber osa (Tribe 8). The leaflets sink vertically down 

 at night. 



Phaseolus vulyaris (Tribe 8). The leaflets likewise sink verti- 

 cally down at night. In the greenhouse the petiole of a young 

 leaf rose 16, and that of an older leaf 10 at night. With 

 plants growing out of doors the leaflets apparently do not sleep 

 until somewhat late in the season, for on the nights of July llth 

 and 12th none of them were asleep ; whereas on the night of 

 August 15th the same plants had most of their leaflets verti- 

 cally dependent and asleep. With Ph. caracalla and Hernan- 

 dtsii, the primary unifoliate leaves and the leaflets of the 

 secondary trifoliate leaves sink vertically down at night. This 

 holds good with the secondary trifoliate leaves of Ph. Eox- 

 burghii, but it is remarkable that the primary unifoliate leaves, 

 which are much elongated, rise at night from about 20 to 

 about 60 above the horizon. With older seedlings, however, 

 having the secondary leaves just developed, the primary leaves 

 stand in the middle of the day horizontally, or are deflected 

 a little beneath the horizon. In one such case the primary 

 leaves rose from 26 beneath the horizon at noon, to 20 above 

 it at 10 P.M.; whilst at this same hour the leaflets of the 

 secondary leaves were vertically dependent. Here, then, we 

 have the extraordinary case of the primary and secondary 

 leaves on the same plant moving at the same time in opposite 

 directions. 



We have now seen that the leaflets in the six genera of Pha- 

 seolese observed by us (with the exception of the primary leaves 

 of Phaseolus Roxburghii) all sleep in the same manner, namely, 

 by sinking vertically down. The movements of the petioles 

 were observed in only three of these genera. They rose in 

 Centrosema and Phaseolus, and sunk in Amphicarpaea. 



Sophora chrysophylla (Tribe 10). The leaflets rise at night, 

 and are at the same time directed towards the apex of the leaf, 

 as in Mimosa pudica. 



Ccesalpinia, Hcematoxylon, Gleditscliia , Poinciana. The leaflets 

 of two species of Csesalpinia (Tribe 13) rose at night. With 

 Hcematoxylon Campechianum (Tribe 13) the leaflets move for- 

 wards at night, so that their midribs stand parallel to the 

 petiole, and their now vertical lower surfaces are turned out- 

 wards (Fig. 153). The petiole sinks a little. In Gleditschia, if 

 we understand correctly Duchartre's description, and in Poin- 



