The beginnings of the orchid family are shrouded in mystery. Since most orchids are epiphytic that is, having aerial roots through which they receive sustenance from the minerals in the moisture laden air of the tropics they have left no traces such as the fossilized remains of ground growing plants. Dr. E. Soysa, writing in Orchid Culture in Ceylon, advances the delightful and plausible, if unproved, theory that orchids antedated the fossil era, but in their love of light ascended trees to escape the advancing jungle.
There they lived, died, dried up, and floated away, leaving no trace. Whatever the genesis of the orchid family, it cannot be doubted that the orchid family is very old, judging both by its great variety and its highly complex structural development, attainable only through the passage of time.
The orchid is among the largest and most highly developed of the plant families, with some fifteen to twenty thousand species. A provident nature has lavished every means to insure the perpetuation of this favorite child. She has provided the flower with all the charm and allure of a fairy princess to win insect vassals to perform the service of cross pollination.
Nature has decreed that the orchid should be dependent on some outside insect agent, and the resultant relation is a beautiful example of cooperation between the plant and animal kingdoms. The highest means of perpetuation in plants, cross pollination is necessary in all but a very few species of orchids. In the few cases of self pollination the seeds are frequently infertile.
The insects performing the service of cross pollination vary with the species and are as diverse as the ingenious contrivances by which the orchids utilize them. It is in every case a reciprocal arrangement, the plant receiving the benefits of fertilization, the insect the largess of food and drink. Each species usually has its particular insect, as is shown by the special means each flower uses to attract its insect.
Darwin first noted a striking example of this specialization. On a trip to South America he had an opportunity to see a plant of Angraecum sesquipedale. This starry white flower, a rare orchid of Madagascar, has a weirdly elongated lip containing a nectary, about eleven inches long, that holds one and a half ounces of the sweet fluid produced by the sugar secreting glands. Darwin immediately predicted that some day a moth with a proboscis at least twelve inches long would be discovered to be responsible for cross pollination of this peculiar orchid.
In time such a moth was found and was duly named Xanthopan morgani praedicta. In this particular alliance it is probable that the moth would starve without the orchid and that the orchid would become extinct without the moth. Such high specialization has insured the purity of species that has marked the progress of the orchid family.
This specialization is reflected in the extremely varied forms of the reproductive organs. These organs lie within the lip, more scientifically known as the labellum, along a fleshy enlargement called the column. The anther bearing stamens are usually sealed together into the column, and a projection of this elongated fleshy organ is the rostellum, whose purpose seems to be to separate the pollen and the stigmatic cavity, thus minimizing the danger of self pollination.
The anthers produce tiny powdery grains of fertile pollen, usually held together by a mysterious viscid fluid that hardens on exposure to air and is not affected by wind or rain. The stigmatic cavity with its receptive ovum (egg) waits for the `marrying` insect to deposit pollen from another flower.
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