--Nectar of certain
flowers unattractive to certain insects.--Industry of bees, and the
number of flowers visited within a short time.--Perforation of the
corolla by bees.--Skill shown in the operation.--Hive-bees profit by the
holes made by humble-bees.--Effects of habit.--The motive for
perforating flowers to save time.--Flowers growing in crowded masses
chiefly perforated.
CHAPTER XII.
GENERAL RESULTS.
Cross-fertilisation proved to be beneficial, and self-fertilisation
injurious.--Allied species differ greatly in the means by which
cross-fertilisation is favoured and self-fertilisation avoided.--The
benefits and evils of the two processes depend on the degree of
differentiation in the sexual elements.--The evil effects not due to the
combination of morbid tendencies in the parents.--Nature of the
conditions to which plants are subjected when growing near together in a
state of nature or under culture, and the effects of such
conditions.--Theoretical considerations with respect to the interaction
of differentiated sexual elements.--Practical lessons.--Genesis of the
two sexes.--Close correspondence between the effects of
cross-fertilisation and self-fertilisation, and of the legitimate and
illegitimate unions of heterostyled plants, in comparison with hybrid
unions.
INDEX.
...
THE EFFECTS OF CROSS AND SELF-FERTILISATION IN THE VEGETABLE KINGDOM.
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