Naturalists are so
much accustomed to behold great diversities of structure associated with the two
sexes, that they feel no surprise at almost any amount of difference; but
differences in sexual nature have been thought to be the very touchstone of
specific distinction. We now see that such sexual differences--the greater or
less power of fertilising and being fertilised--may characterise the co-existing
individuals of the same species, in the same manner as they characterise and
have kept separate those groups of individuals, produced during the lapse of
ages, which we rank and denominate as distinct species.
CHAPTER VII.
POLYGAMOUS, DIOECIOUS, AND GYNO-DIOECIOUS PLANTS.
The conversion in various ways of hermaphrodite into dioecious plants.
Heterostyled plants rendered dioecious.
Rubiaceae.
Verbenaceae.
Polygamous and sub-dioecious plants.
Euonymus.
Fragaria.
The two sub-forms of both sexes of Rhamnus and Epigaea.
Ilex.
Gyno-dioecious plants.
Thymus, difference in fertility of the hermaphrodite and female individuals.
Satureia.
Manner in which the two forms probably originated.
Scabiosa and other gyno-dioecious plants.
Difference in the size of the corolla in the forms of polygamous, dioecious, and
gyno-dioecious plants.
There are several groups of plants in which all the species are dioecious, and
these exhibit no rudiments in the one sex of the organs proper to the other.
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