Plain Facts for Old and Young

by John Harvey Kellogg

In many instances the action of plants seems almost to be prompted by intelligence. At the proper moment, the corolla contracts in such a way as to bring the stamens nearer to the stigma, or in contact with it, so as to insure fecundation. In some aquatic plants the flowers elevate themselves above the surface of water while the process of fecundation is effected; submerging themselves again immediately afterward.

Other very curious changes occur in flowers of different species during the reproductive act. The stigma is observed to become moistened, and even to become distinctly odorous. Often, too, it becomes intensely congested with the juices of the plant, and sometimes even acquires an uncommon and most remarkable degree of contractility. This is the case with the stigma of the tulip and one variety of sensitive plant, and is in these plants observed to occur not only after the application of the pollen to the stigma, but when excited by any other means of stimulation. The flowers of some plants, during and after fecundation, also show an increase of heat, in some cases so marked as to be readily detected with the thermometer. This is said to be the case with the arum of Italy.

In some plants in which the pistil is longer than the stamens, thus elevating the stigma above the anthers, the female organ is often observed to bend over and depress itself so as to come within reach of the anthers.

In most instances the fecundation of flowers is chiefly effected through a purely mechanical process, though in these cases also we see a wonderful adaptation of parts to conditions.

When the male and female parts of flowers are situated on different plants, as is the case in the willow, the poplar, the melon vine, and many other species, the pollen of the male flower is wafted by the wind or gentle breeze to the stigma of the female flower, which will usually be found at no very great distance, although fertilization may take place in this way at very considerable distances. Bees, moths, and many other species of insects, serve a very important purpose in this work, transporting the fertilizing dust upon their wings, antennæ, sucking-tubes, and feet. Small birds, and even the humble snail, which would scarcely be credited with any useful function, are also very serviceable in the same direction. The part performed by insects in the reproductive process of many plants is so great that they have been very poetically termed "the marriage priests of flowers."

Nature provides for thorough fecundation in these cases by placing the plants which bear the male and the female flowers near each other. This fact accounts for the unproductiveness of certain varieties of strawberries unless mixed with plants of some other variety, it being well known to nursery-men that some varieties produce only the female parts of flowers.

Modes of Fecundation in Animals.—The modes by which fecundation is effected in animals are still more various and wonderful than in plants. In some of the lower animals, as in most fish and reptiles, both elements are discharged from the bodies of the parents before coming in contact, there being no contact of the two individuals. In this class of animals the process is almost wholly analogous to fecundation in those plants in which the male and female flowers are on different plants or different parts of the same plant. In the female fish, a large number of ova are developed at a certain season of the year known as the spawning season. Sometimes the number reaches many thousands. At the same time, the testicles of the male fish, which are contained within the abdominal cavity, become distended with developed zoösperms. When the female seeks a place to deposit her eggs, the male closely follows; and as she drops them upon the gravelly bottom, he discharges upon them the zoösperms by which they are fecundated. The process is analogous to some species of frogs. When the female is about to deposit her eggs, the male mounts upon her back and rides about until the eggs are all deposited, discharging upon them the fertilizing spermatozoa as they are laid by the female.

In higher orders of animals, fecundation takes place within the generative organs of the female by contact between the male and the female organs. To effect this, there are necessitated certain accessory organs, the penis in the male and the vagina in the female.