GYMNOSPERMS Conifer pollen, instead of being formed in stalked anthers as is that of Angiosperms,' is produced in two or more pollen sacs on the lower side of the male cone-scales. The pollen grains are large and often bear two conspicuous air-filled bladders which decrease the density of the particle and so retard its fall under the influence of gravity.
In P-rnus, cone-scales of the erect male cone separate as they mature, and pollen shed from the paired sacs falls into small hollows on the upper surface of the cone-scale below. From these hollows the pollen is blown away when the wind reaches sufficient velocity. Some other conifers have hygroscopic mechanisms protecting their pollen from rain and allowing its release only in dry weather. In Tarns, Thuja, Cupressus, and Jim /perils, the pollen is not winged. In 7aiperus the expanded ends of the cone scales interlock closely in damp weather, separating again in dry air and allowing pollen to be blown out.