pods--Heliotropism and apheliotropism modified forms of circumnutation--
Steps by which one movement is converted into the other--
Transversal-heliotropismus or diaheliotropism influenced by epinasty, the
weight of the part and apogeotropism--Apogeotropism overcome during the
middle of the day by diaheliotropism--Effects of the weight of the blades
of cotyledons--So called diurnal sleep--Chlorophyll injured by intense
light--Movements to avoid intense light...418-448


CHAPTER IX.

SENSITIVENESS OF PLANTS TO LIGHT: ITS TRANSMITTED EFFECTS.

Uses of heliotropism--Insectivorous and climbing plants not heliotropic--
Same organ heliotropic at one age and not at another--Extraordinary
sensitiveness of some plants to light--The effects
[page ix.]
of light do not correspond with its intensity--Effects of previous
illumination--Time required for the action of light--After-effects of
light--Apogeotropism acts as soon as light fails--Accuracy with which
plants bend to the light--This dependent on the illumination of one whole
side of the part--Localised sensitiveness to light and its transmitted
effects--Cotyledons of Phalaris, manner of bending--Results of the
exclusion of light from their tips--Effects transmitted beneath the surface
of the ground--Lateral illumination of the tip determines the direction of
the curvature of the base--Cotyledons of Avena, curvature of basal part due
to the illumination of upper part--Similar results with the hypocotyls of
Brassica and Beta--Radicles of Sinapis apheliotropic, due to the
sensitiveness of their tips--Concluding remarks and summary of chapter--
Means by which circumnutation has been converted into heliotropism or