This section is from the book "The Gardener's Monthly And Horticulturist V23", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
Read before the American Association for the Advancement of Science, Saratoga, August, 1879, BY THOMAS MEEHAN, Professor of Botany in the State Board of Agriculture of Pennsylvania, and Fellow of the Association.
Students of nature, who have thoughtfully observed, must have noted at least two great objects in the creation of sex. The first and leading one is evidently to insure variation; the second to aid and assist reproduction. But our text-books say little of the first; while every behavior of flowers is regarded as relating to the last, and hence we have so much said and written on the advantages of cross-fertilization, as if reproduction were the sole end and aim of sex.
That reproduction is not the sole end of sex is apparent from the fact that reproduction by cell division is more common in vegetation than reproduction by seed. Bulbs, tubers, rhizomes and other subterranean structures, with bulblets, runners and other arrangements above ground are familiar examples. Many plants with colored corollas rarely seed, while some never do. Of these I might name Ranunculus Ficaria, Lilium tigrinum, the Horse Radish, Cochlearia armoraica, etc.; and again are those which depend on insect or similar agency for polleniza-tion, and though apparently as a result bearing seed abundantly, yet rarely producing plants in nature from these seeds. Of these last, I need only refer to Yucca and Orchideae as the best known of the class dependent on insect fertilization. The terrestrial orchideae of the United States mostly fruit in great abundance, and there are many thousands of seeds in each capsule; yet my researches have rarely been rewarded by plants that I could believe to be seedlings; while in nearly all cases the relation by offsets from a parent plant was plain.
On the other hand, orchid locations are declining, and Yucca confines its species to comparatively limited locations, apparently raising a crop of seeds more for the sake of feeding the larvae of the Yucca moth, than as an aid in plant distribution. So far as reproduction is concerned, it will not be denied that millions on millions of seeds are created in vain, that thousands of millions of flowers bloom uselessly, that volumes of odor and tons and tons of pollen are given to the winds and to the insects, without any possible benefit to the individual, which could be made to increase without any of these productions of no conceivable benefit to the race, except as might arise from some imaginary good from cross-fertilization. We see from these simple considerations that sex can have but a very remote relation to the good of the individual or the race; and we may reasonably look about for some more important service which sex is to render.
We find this in variety. This is essential to our present conditions of existence. Imagine the higher order of animals increasing by division! Each would be exactly like its parent. Mr. Smith could not tell himself from Mr. Brown. But the union of two distinct individuals, and each individual with varying powers of transmitting identity, leads to infinite variety, by which each can clearly distinguish that which is his from what is his neighbor's. Variety is a greater necessity to sentient beings than to inanimate things; hence we see that propagation through sex is imperative among them. But it can, in this respect, make no difference to a plant. It is of no consequence to one blade of grass that another blade should be or not be just like it. But it is of great consequence to the animal life that is to feed on them. Each kind is made to prefer some kinds of fruit and vegetables, which must have distinct characters in order to be easily recognized; and hence we have at once a good reason for form, color, fragrance and the infinite variety these productions give rise to. If this view be correct, and I cannot conceive that it can be controverted, it puts a new view on modern teleology.
In all the discussions on the various arrangements of plants and animals, we hear only of what good is to result to the individual or to the race. This is the essential character of the doctrine of natural selection. But on the principle that I have sketched out - the principle of variation - we see plants and animals not working merely for their own good, although that is incidentally involved, but for the good of generations yet unborn, and in which they can have no interest. Indeed, following the inexorable law of variation, plants may be said to be laboring to make themselves distinct from each other so that the various animals may be better able to recognize and consume them. They must necessarily be under the control and direction of an outside power, which clearly foresees that there will be mouths, and judgment required to select the food which is to go into them; all of which would be useless unless plants were forced into a variety, which is thus to enable them to be the more easily sacrificed when the proper time arrives. Of course the selfish views embodied in the modern doctrines of teleology must be incidentally true. No individual would work unless it supposed it was working for its own good. Pleasure must be a condition of existence.
This also must be a universal law, and "natural selection" so far to be conceded. But this law must of necessity be limited. It is not for the good of a plant that it should be eaten by an animal; but it is perfectly consistent with the law of universal good that it should have just enough of thorns, or bitterness, or some other measures of defence to keep the race from being utterly annihilated.
May we not conclude from all this that variation and not reproduction is the one great law to which we are primarily to refer all sexual phenomena; that reproduction occupies only a place subservient to this law; and if so may we not proceed to review the theories which have been established under a mistaken idea of the order of things?
I propose to examine, but I shall confine my-self here to only one subject; indeed to but a part of that subject, namely, the relation which odor in flowers bears to modern theories of cross-fertilization.
(To be continued.)