( Originally Published 1943 )
In describing grasses as flowering plants we probably caused you to wonder what part of the grasses were flowers. And where these flowers hide themselves. The fact is, that most grasses contain perfect flowers. That is, they contain both pistils and stamens in the same flower. They are in-conspicuous because of their small size and their blending shades of green.
The average size of a grass floret, as a single grass flower is called, is three-eighths of an inch. Nevertheless, in this small floret there is usually three well developed stamens whose anthers give off as many as 20,000 pollen grains each. Florets also contain, on the average, two pistils for receiving pollen grains and production of seeds. Each floret is enclosed in what is known as a spikelet (Fig. 4). These spikelets are bunched together along the upper part of a stem of the grass plant to make up what is called a flowering head. This part of a grass plant is what makes up the hay and is distinct from the flat green blades of grass that every one knows as grass. The' flowering head of a grass stem contains from 100 to i,000 spikelets, and various grass plants produce from io to 15 stems with flowering heads. Thus a single grass plant may be calculated to produce 20,000 pollens times 3 stamens, times 1,000 spike-lets, times 15 stems or 900,000,000 pollen grains. And that's a lot of hay fever.
When the grass florets are ripe they wait for a dry sunny day in May, June, or July and discharge their pollen in one burst. After this, each floret closes and soon withers. This is repeated at the same hour on succeeding days and continues until all the flowers of a plant have shed their pollen. The grasses for some unknown reason seem to have an exact time of day for shedding their pollen. Most of them pollinate between 6 and 7 a.m., oats between 2 and 4 p.m., and wheat between 4 and 5 p.m. Hay fever sufferers should be guided accordingly.
Most grasses are wind-pollinated. The cereals, such as barley, oats, wheat, and rice, are self-pollinated and consequently cause little hay fever. An exception to this is rye, which is wind-pollinated. But like the other cereals its pollens are too, large to be buoyant, however, in Germany, where rye is extensively cultivated, it causes a considerable amount of spring hay fever.
In general the grass pollens are not blown around nearly as much as ragweed pollens. As explained by Durham, this is due to the fact that they are large, have a smooth surface, and also retain moisture readily which makes them too heavy to float easily. Exposure of slides at various heights shows much greater grass pollen concentrations close to the ground. This should act as a warning to summer hay fever sufferers against picnicking in grass fields during the pollinating periods. If you are a golf addict you should seek out a course whose greens are cut short and are not giving off pollens at the time you are slicing into the rough. Moreover, it is not a wise policy for such an individual to live in the suburbs where grass fields are abundant. In the case of sensitivity to grass pollens, living in the cities offers a measure of protection because of the relative lack of buoyancy of these pollens.