Wind Pollination Anemophily

WIND POLLINATION (ANEMOPHILY) The method of pollination of the earlier and more primitive flowers was probably by the wind, the insect pollinated flowers being derived from them in later stages of evolution. Some flow ers such as plaintain and meadow rue mentioned above, are al most certainly anemophilous by reduction, all their congeners being entomophilous ; other cases are Poterium among the Rosa ceae and Kerguelen's Land cabbage (q.v.) among the Crucif erae.

Characters of Anemophilous Flowers.

These are such as might be expected. The flowers are usually inconspicuous (the corolla being commonly absent) for there is no advantage in their being easily seen, and they are without the scent or nectar so common in flowers visited by insects. Furthermore there is usually no tubular formation of the flower and no irregularities. On the other hand these wind-pollinated flowers form large quantities of pollen, since the greater proportion when consigned to the air must necessarily be lost. The large quantity of pollen produced by pines and other conifers is well known; in these plants the nu merous stamens are massed in male cones often of considerable size, though smaller than the female cones. In other families, such as the grasses, Cyperaceae, Urticaceae, the number of stamens in each flower is small but the anthers are large. Again, in these

flowers the pollen is dry and powdery and does not stick together in small masses as in entomophilous flowers ; this enables the pollen to blow about easily. The pollen in this type of flower must be easily removed by the wind ; the absence of floral en velopes facilitates this and so do the pendulous catkins (hazel, plane, etc.) which can sway in the wind. In addition the filament of the stamen is usually long so that the anthers hang out of the flower, and are also versatile (see FLOWER) so that the pollen is easily shaken from them.

Another common characteristic of the flowers in question is that the stigma is much larger and rougher than that of entomophilous flowers and it is freely exposed to the air so as to increase the chance of reception of the pollen ; in maize, for example, the stigma is of very great length. In many catkin-bearing plants the flowering stage occurs before the leaves appear, so that accidental interception of pollen by the leaves is avoided. As already stated dichogamy is quite common in anemophilous flowers but proter ogyny is much more common than protandry.