344 



MODIFIED CIBOUMNUTATION. 



Chap. VII 



and alhifrons, though observed out of doors and in the green- 

 house, did not change the poeition of their leaves sufficiently at 

 night to be said to sleep. From observations made on two 

 sleeping species, it appears that, as with Tiopmolum majus, the 

 leaves must be well illuminated during the day in order to sleep 

 at night. For several plants, kept all day in a sitting-room 

 with north-east windows, did not sleep at night ; but when the 

 pots were placed on the following day out of doors, and were 

 brought in at night, they slept in the usual manner. The trial 

 was repeated on the following day and night with the same 

 result. 



Some observations were made on the circumnutation of the 

 leaves of L. luteus and arb'ireus. It will sufBoe to say that the 

 leaflets of the latter exhibited a double oscillation in the course 

 of '24 h. ; for they fell from the early morning until 10 15 a.m., 

 then rose and zigzagged greatly till 4 p.m., after which hour the 

 great nocturnal fall commenced. By 8 a.m. on the following 

 morning the leaflets had risen to their proper height. We have " 

 seen in the fourth chapter, that the leaves of Lupinus speciosus, 

 which do not sleep, circumnutate to an extraordinary extent, 

 making many ellipses in the course of the day. 



Cytisus (Tribe 2), Trigonella and Medicago (Tribe 3).— Only 



Fig. 139. 



A. B. 



iledicago marina ■ A. leaves during the day ; B, leaves asleep at night. 



a few observations were made on these three genera. The 

 petioles on a young plant, about a foot in height, of Cytisus 

 fragrans rose at night, on one occasion 23° and on another 33°. 

 The three leaflets alsj bend upwards, and at the same time 



