. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. FLOWERS 43. Pod of yucca pierced by the Pronuba. gathers pollen from an anther, flies away with this load to an- other flower, there deposits an egg in the ovary of the pistil, and then rubs its load of pollen over the stigma of the flower. The young hatch out and feed on the young seeds which have been fertilized by the pollen placed on the stigma by the mother. They eat some of the developing seeds and then bore out of the seed pod and escape to the ground, leaving the plant to develop th
. Elements of biology; a practical text-book correlating botany, zoology, and human physiology. Biology. FLOWERS 43. Pod of yucca pierced by the Pronuba. gathers pollen from an anther, flies away with this load to an- other flower, there deposits an egg in the ovary of the pistil, and then rubs its load of pollen over the stigma of the flower. The young hatch out and feed on the young seeds which have been fertilized by the pollen placed on the stigma by the mother. They eat some of the developing seeds and then bore out of the seed pod and escape to the ground, leaving the plant to develop the remaining seeds with- out molestation. The fig insect (Blastophaga grossorum) is another member of the insect tribe that is of considerable economic importance. It is only in recent years that the fruit growers of Cali- fornia have discovered that the fertilization of the female flowers is brought about by a gall fly which bores into the young fruit.^ Pollination by the Wind. — Not all flowers are dependent upon insects for cross-pollination. Many of the earliest of spring flowers appear almost before the insects do. These flowers, needing no conspicuous colors or showy corolla to attract insects, often lack this part altogether. In fact we are apt to entirely overlook the flowers which appear in the spring upon our common forest and shade trees. In many trees, as, for ex- ample, the willow, the flowers appear before the leaves come out. Such flowers are dependent upon the wind to carry pollen from the stamens of one flower to the pistil of another. Most of our com- mon trees, oak, poplar, maple, and others, are cross-pollinated almost entirely by the wind. Among the adaptations that a wind-pollinated flower shows are: (1) The development of very many pollen grains to each ovule. In one of the insect-pollinated flowers, that of the night- blooming cereus, the ratio of pollen grains to ovules is about eight to one. In flowers which are to be pollinated by the wind, a large n
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