Relation Of Pollination To The Cause Of Hay Fever
( Originally Published 1943 )
In the above description we passed over the process of pollination by indicating it as the method whereby pollen grains from the stamen are transferred to the stigmas of the flowers. While this is true, there are several methods by which this transfer is accomplished in the various kinds of plants. A complete knowledge of these methods is of utmost importance in understanding how pollens may, or may not, cause hay fever.
When the pollen from the stamen reaches the stigma of the same flower, the plant is said to be self-pollinated. This can only be accomplished by hermaphrodite flowers which contain both the male stamens and female pistils within the same floral envelope. Examples of this type are certain violets and the wood sorrel plant. Since these pollens are not spread around they obviously could not be responsible for causing hay fever.
When the pollens from the stamen of one flower reach the stigmas of another flower, the plants are said to be cross pollinated. This method is by far the most common among flowering plants. The agents of the transfer of pollen in cross pollination are wind, insects and water. In plants which grow in lakes or rivers the pollens float or drift from the stamens to the stigmas. The eel-grass and water weed are examples of water pollinated plants. As in the case of the self-pollinated plants, these can have no bearing on the cause of hay fever.
Insect Pollination. The most popular and the most decorative flowers invariably depend upon bees, butterflies, beetles, moths, ants, flies or dragon flies to accomplish pollination.. To attract these insects they have beautiful patterns of bright colors, scented perfumes, and glands for supplying the insects with sweet nectar. Added to this are the many wondrous mechanisms of these flowers to make certain that the insects will carry pollens on their wings, head, feet and body. Amazing, are the adaptations of such flowers as the Snap Dragon, Lady Slipper, and Venus Fly Trap, whose very names suggest the mechanisms.
Fascinating indeed, is the description of the iris with its yellow and white guide lines on large blue petals which serve as landing field and guide lines, for leading the bee to the nectar in the bottom of the flower. The stigma of the iris is placed in such a position that, as the bee follows the nectar guides it has to bend the stigma down and brush its back against the stigma. In this way the bee is made to deposit the pollen that it gathered from a previous plant. Then as the bee continues down into the heart of the flower she brushes past the anther causing the sticky pollen to adhere to her back. After obtaining her fill of nectar the bee leaves the iris by the path she entered. But in the meantime the stigma turns up so that it does not disturb the newly received pollen on the back of the re-treating bee.
Since every insect-pollinated plant has some provision to insure its successful pollination, we could describe many such procedures. And although extremely interesting, we are not primarily concerned with these phenomena in this book. However, these pollinating mechanisms are responsible for excluding the decorative flowers as important causes of hay fever. Due to their efficient pollinating techniques these flowers produce only a fraction of the amount of pollen as the wind pollinating plants. Because the pollen has to adhere to the insects it is sticky and generally clumps together making it too heavy to be wafted around in the atmosphere.
Wind Pollination. The wind pollinated flowers are mostly dull in color, unperfumed, and haven't any nectar. Included in this class are many trees, grasses, cereals, and weeds. They do not attract insects and therefore have to depend upon the wind to transport their pollens from one plant to another. This method is obviously a hit-or-miss affair. The chances of one pollen grain from a ragweed plant reaching the stigma of another ragweed plant is extremely poor. To compensate for their inefficient method, the wind-pollinating plants spread billions and billions of pollen grains into the air. One investigator calculated that a giant ragweed plant produced about eight billion pollen grains in five hours and that a field of grass in its pollinating stage produced eight million pollen grains per square foot of surface. Contrasted to this is the estimate that it takes only 25 pollen grains per cubic yard of air to produce hay fever symptoms. Now calculate your own chances of escaping hay fever in an area where ragweed plants flourish. Regardless of how hopeless escape appears, if we are to be successful in our campaign against the eradication of hay fever, we must continue to study in detail the plants responsible for producing hay fever symptoms.
A SCIENTIFIC PRINCIPLE
In tackling a scientific problem the methods of science are similar to those employed in any successful attack. Similar in fact, to a basic fundamental utilized in fighting a war. This fundamental consists of learning as many de-tails as possible about the nature of your allies and your enemies before attempting to deal with them. The Generals of the United States Military forces follow this principle constantly. As part of their preparation for the over-seas expedition to North Africa, the Army issued to all soldiers a Pocket Guide to North Africa. This was not a map, but rather a description of the appearance, language, religion, habits, customs and character of their future Mohammedan allies in North Africa. The United States Army issued similar information to their troops concerning the nature and character of their German and Japanese enemies. We must proceed in a like manner in our attack on hay fever.
HAY FEVER NOT DUE TO ROSES AND GOLDENROD
Although pollination represents only one phase of our study of the entire hay fever problem, by understanding it, we have learned a great deal which is of value in helping to combat hay fever. For instance, by learning that the goldenrod plants are insect pollinated, and that their sticky pollens are too heavy to float any distance in the air, science has dispelled the original erroneous concept that the goldenrod plant was the cause of autumn hay fever. Similarly accused and vindicated was the rose. This beautiful flower was done an even greater injustice by having the early summer type of hay fever named after it and called rose-fever. Like goldenrod, the rose is an insect-pollinated plant. Its pollens do not float in the air. Thus we arrive at the conclusion that neither the rose, the goldenrod, nor any other insect-pollinated plant produces hay fever symptoms except on close proximity or when these flowers have been cut, permitted to dry, and the pollens shaken into the air in. the vicinity of a sensitive person.
The false impression that goldenrod and roses are chiefly responsible for hay fever is prevalent in the minds of many thousands. Among this group is a surprisingly large number of persons with hay fever. Many of these individuals know in a general way that hay fever is due to the blooming of flowers, pollination, or the spread of pollen. Since the rose blooms at the time when early summer hay fever, due to grasses, begins, it is easy to understand how the early summer hay fever came to be called mistakenly, "rose-fever" and "rose-cold." The goldenrod in its turn, flourishes far and wide with its golden yellow color at the period when the ragweed spreads its pollen. Thus accounting for the popular misunderstanding as to its relation to the cause of hay fever.
It seems to us that reliable and widespread information about the nature of pollens would help to clear up popular misconceptions and serve to answer many questions not explained by the mere knowledge that hay fever is caused by pollens. Perhaps you are among those who have asked, "What are these pollens? What do they look like? Can they be recognized easily? How do they get around? Can they travel far? How long can they live? How long can they produce irritations? What happens to them after the hay fever season? Of what do the pollens consist? Are they poisonous? Are the hay fever pollens different from the ones that do not cause hay fever?" From the time of the ancients to the present day, observations and investigations have been made in order to obtain the answers to these very questions.