26).--The
* 'Trans. Bot. Soc. Edinburgh,' vol. xiii. p. 32. With respect to the
origin of the Swedish turnip, see Darwin, 'Animals and Plants under
Domestication,' 2nd edit. vol. i. p. 344.
[page 231]
terminal shoot of a young plant, growing very vigorously, was selected for
observation. The young leaves at first stand up vertically and close
together, but they soon bend outwards and downwards, so as to become
horizontal, and often at the same time a little to one side. A filament was
fixed to the tip of a young leaf whilst still highly inclined, and the
first dot was made on the vertical glass at 8.30 A.M. June 13th, but it
curved downwards so quickly that by 6.40 A.M. on the following morning it
stood only a little above the horizon. In Fig. 96
Fig. 96. Dianthus caryophyllus: circumnutation of young leaf, traced from
10.15 P.M. June 13th to 10.35 P.M. 16th. Apex of leaf stood, at the close
of our observations, 8 3/4 inches from the vertical glass, so tracing not
greatly magnified. The leaf was 5 1/4 inches long. Temp. 15 1/2o - 17 1/2o
C.
the long, slightly zigzag line representing this rapid downward course,
which was somewhat inclined to the left, is not given; but the figure shows
the highly tortuous and zigzag course, together with some loops, pursued
during the next 2 ? days.
Pages:
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390