(14.) Drosera rotundifolia (Droseraceae, Fam. 85).--The movements of a
young leaf, having a long petiole but with its tentacles (or gland-bearing
hairs) as yet unfolded, were traced during 47 h. 15 m. The figure (Fig.
105) shows that it circumnutated largely, chiefly in a vertical direction,
making two ellipses each
[page 238]
day. On both days the leaf began to descend after 12 or 1 o'clock, and
continued to do so all night, though to a very unequal distance on the two
occasions. We therefore thought that the movement was periodic; but on
observing three other leaves during several successive days and nights, we
found this to be an error; and the case is given merely as a caution. On
the third morning the above leaf occupied almost exactly the same position
as on the first morning; and the tentacles by this time had unfolded
sufficiently to project at right angles to the blade or disc.
Fig. 105. Drosera rotundifolia: circumnutation of young leaf, with filament
fixed to back of blade, traced from 9.15 A.M. June 7th to 8.30 A.M. June
9th. Figure here reduced to one-half original scale.
Pages:
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399