PLANTS VALUABLE ONLY FOR POLLEN
There are thousands of species of the higher plants which never secrete nectar, but they all produce pollen. As has been shown in the chapter describing plants which are valuable only for pollen, they may be divided into two groups, one of which is pollinated by insects and the other by the wind. Nectarless flowers pollinated by insects are called pollen-flowers, and are often large and bright-colored, as the poppy and the rose. Insects visit them to gather or feed on the pollen. The nectarless wind-pollinated flowers also produce pollen abundantly. Since they rely upon the wind rather than upon insects nectar would be of no advantage to them. The number of flower-visiting insects is wholly insufficient to pollinate the myriads of little blossoms put forth by the grasses and sedges and vast forests of birches, poplars, oaks, hickories, and beeches. The cereals — wheat, oats, barley, rye, rice; and com — cover 225,000,000 acres, and manifestly must depend on wind-pollination. Beekeepers should be able to recognize the plants which are valuable only as sources of pollen, lest they mistake them for honey plants. Moreover, from the foliage of many hardwood trees great quantities of honey-dew are gathered, which is often mistaken for floral honey. Thus Brown in his Chemical Analysis of American Honeys gives an analysis of the “floral honey” of the poplar (Populus) and the oak (Quercus), both wind-pollinated trees; but the chemical constituents of these honeys, as well as their polarization, show that they are honey-dew honeys.
While all species of the higher plants produce pollen, nevertheless there is a great number of flowers from which it is wholly absent. For example, there are many plants which have two forms of flowers, one containing the stamens and the other the pistils (alder, willow, poplar, cucumber, squash, gallberry, and tupelo); no pollen can, of course, be found in the pistillate flowers. This division of the essential members prevails very largely among the sedges, many hardwood trees, and many homely weeds and herbs. In the immense family of the Compositae, which includes the thistles, asters, and goldenrods, the marginal flowers of the heads in many genera have lost their stamens, and often also the pistils as well. They have been converted into long bright-hued straps, which frequently differ in color from the disc florets, and whose sole function is to render the flower-cluster conspicuous for the purpose of attracting insects. For the same reason the marginal flowers of the flat-topped flower-cluster of the hobblebush (Viburnum alnifolium) have become large and white, and have lost both stamens and pistils, while the inner, nectar-bearing flowers still remain small and green. Under cultivation scores of flowers have become double by the conversion of the stamens into petals, as the double buttercups, roses, and peonies. There are thus myriads of flowers which are wholly devoid of pollen.
The following list of flowers will be found of two-fold value: it will enable beekeepers to recognize plants, often exceedingly abundant, which are nectarless. and thus avoid building false hopes of a honey flow on their bloom; and it will afford them information in regard to many valuable sources of pollen. It should also prevent them from mistaking an inflow of honey-dew from hardwood trees