e two
principal agents of conveyance are winds and insects. Most flowers are
in their whole structure adapted either to the one or to the other.

334. =Wind-fertilizable or Anemophilous= flowers are more commonly
dioecious or monoecious, as in Pines and all coniferous trees, Oaks, and
Birches, and Sedges; yet sometimes hermaphrodite, as in Plantains and
most Grasses; they produce a superabundance of very light pollen,
adapted to be wind-borne; and they offer neither nectar to feed winged
insects, nor fragrance nor bright colors to attract them.

335. =Insect-fertilizable or Entomophilous= flowers are those which are
sought by insects, for pollen or for nectar, or for both. Through their
visits pollen is conveyed from one flower and from one plant to another.
Insects are attracted to such blossoms by their bright colors, or their
fragrance, or by the nectar (the material of honey) there provided for
them. While supplying their own needs, they carry pollen from anthers to
stigmas and from plant to plant, thus bringing about a certain amount of
cross fertilization. Willows and some other dioecious flowers are so
fertilized, chiefly by bees. But most insect-visited flowers have the
stamens and pistils associated either in the same or in contiguous
blossoms. Even when in the same blossom, anthers and stigmas are very
commonly so situated that under insect-visitation, some pollen is more
likely to be deposited upon other than upon own stigmas, so giving a
chance for cross as well as for close fertilization. On the other hand,
numerous flowers, of very various kinds, have their parts so arranged
that they must almost necessarily be cross-fertilized or be barren, and
are therefore dependent upon the aid of insects. This aid is secured by
different exquisite adaptations and contrivances, which would need a
volume for full illustration. Indeed, there is a good number of volumes
devoted to this subject.[1]

336. Some of the adaptations which favor or ensure cross fertilization
are peculiar to the particular kind of blossom. Orchids, Milkweeds,
Kalmia, Iris, and papilionaceous flowers each have their own special
contrivances, quite different for each.

337. Irregular flowers (253) and especially irregular corollas are
usually adaptations to insect-visitation. So are all _Nectaries_,
whether hollow spurs, sacs, or other concavities in which nectar is
secreted, and all _nectariferous glands_.

338. Moreover, there are two arrang