246 CIKCUMNUTATION OF LEAVES. Chap. IV. 



day the leaf descended from 8.20 a.m. till 7.15 p.m., then zigzagged 

 and ascended greatly during the night. On the morning of the 

 20th the leaf was probably beginning to descend, though the 

 short line in the diagram is horizontal. The actual distances 

 travelled by the apex of the leaf were considerable, but could 

 not be calculated with safety. From the course pursued on the 

 second day, when the plant had accommodated itself to the light 

 from above, there cannot be much doubt that the leaves undergo 

 a daily periodic movement, sinking during the day and rising 

 at night. 



(18.) MuHsia cli-malis (Compositae). — The leaves terminate in 

 tendrils and circumnutate like those of other tendril-bearers ; 

 but this plant is here mentioned, on account of an erroneous 

 statement * which has been published, namely, that the leaves 

 sink at night and rise during the day. The leaves which 

 behaved in this manner had been kept for some days in a 

 northern room and had not been sufficiently illuminated. A 

 plant therefore was left undisturbed in the hot-house, and three 

 leaves had their angles measured at noon and at 10 p.m. All 

 three were inclined a little beneath the horizon at noon, but one 

 stood at night 2°, the second 21°, and the third 10° higher than 

 in the middle of the day; so that instead of sinking they rise 

 a little at night. 



(19.) Cyclamen Persicum (Primulacese, Fam. 1.35). — A yomig 

 leaf, 1'8 of an inch in length, petiole included, produced by an 

 old root-stock, was observed during three days in the usual 

 manner (Fig. 110). On the first day the leaf fell more than after- 

 wards, apparently from adjusting itself to the light from above. 

 On all three days it fell from the early morning to about 7 p.m., 

 and from that hour rose during the night, the course being 

 slightly zigzag. The movement therefore is strictly periodic. 

 It should be noted that the leaf would have sunk each evening 

 a little lower down than it did, had not the glass filament rested 

 between 5 and 6 p.m. on the rim of the pot. The amount of 

 movement was considerable ; for if we assume that the whole 

 leaf to the base of the petiole hecame bent, the tracing would 

 be magnified rather less than five times, and this would give 

 to the apex a rise and fall of half an inch, with some lateral 

 movement. This amount, however, would not attract attention 

 ivithout the aid of a tracing or measurement of some kind. 



• 'The Movomonls imd Ilubits of Climbing Plants,' 1875, p. 118. 



