stanced the datura (henbane) as one of those plants in which the action of the pollen on the stigma is very observable. Modern observation has proved most conclusively that the same principle holds good with all plants, and that fecundation is effected in precisely the same manner with all plants. We therefore use Brongniart's figures to illustrate this wonderful phenomenon.

Fig. 4 represents a vertical section of a stigma of datura, showing the tubular sacs after fecundation, the pollen tubes running through all its

thicknesses. These tubular sacs are for the most part already filled with granules (grains of pollen), and are easily distinguished from the tissue of the stigma by their brownish color and opacity. In referring to this figure Brongniart says: "I could not find a better comparison for one of these stigmata than a pin-cushion entirely filled with pins stuck into it up to the head." You will understand the extent to which this has been magnified when I tell you that the whole stigma is not half as large as one of the pollen grains here represented.

Fig. 5 is intended to show the same arrangement in the same plants still

more strongly magnified. The grains of pollen and the pollen tubes are still more enlarged, the better to show the passage of the tube through the substance of the stigma.

These pollen tubes elongate themselves by a most remarkable vegetative process, insinuating themselves into the interstices of the cellular tissue, which has been designated

from this cause the conducting tissue, and that, doubtless, by which it is nourished.

Occupying the center of the style, this tube traverses its whole length, entering into the ovary, as is shown by Fig. 6, and is there brought into contact with the ovules.

To simplify this statement, let us say that these pollen tubes enter through the folds, as they may be termed, of the female organ in precisely the same manner as sexual intercourse in all animals is effected. That active principle of reproduction known as spermatozoa must be as systematically conveyed in the vegetable as in the animal life. The birth of a seed is not the result of accident, but the effect of a wisely ordained cause. Every single seed produced on a plant is the result of a separate and independent impregnation. One pollen grain representing a male plant impregnates but one womb,which in its turn contains but a single seed.

This is shown more plainly by Fig. 7, which illustrates a

FIG. 7.

120

section of the male and female organs entire, and is intended to point out the long course followed by the pollen tubes in penetrating from the stigma to the interior of the ovary, where each of them comes in contact with the ovules.

If you wish to fully appreciate the harmonies of nature, to understand the precision and care that are exercised for the propagation of the species, you

can have no more beautiful or interesting study than is to be found in our corn-fields. You all know very well that if the pollen grain that is formed on the tassel does not fall upon the silk there will be no corn upon the cob ; that is, if a single silk is missed there will be a vacancy in the family circle. Each silk-which bears the same relation to the corn plant that the vagina does to animal forms-receives the pollen grain upon its stigma, and conducts it through its entire length to the ovules, so systematically arranged on the cob, the home of this colony of plants.

While the corn furnishes us with a most interesting study in the phenomena of plant life, our interest becomes absorbed in wonder when we examine the tobacco, the petunia and other allied plants. A capsule of tobacco contains, on an average, 2,500 seeds. In order to produce these there must be 2,500 impregnations, all of which are effected within a period not to exceed twenty-four hours, and in a space less than one-sixteenth of an inch in diameter. The style containing this vast number of passages is, in some of the species, nearly two inches in length, and with a diameter not to exceed one-thirty-second part of an inch. Thus we see 2,500 families dwelling together in a space scarcely visible to the naked eye, carrying on in the most perfect manner all the operations essential for the reproduction of the species.

Neither does wonder and admiration cease here. Observation and experiment have proven conclusively that plants discriminate in their selection for the purposes of reproduction. This theory, or, more properly, principle, in the phenomena of plant life, our time will not permit us to advocate. We can not, however, dismiss this part of our subject without referring to the manner of impregnation by that most singular aquatic plant, the Vallisneria spirales, commonly known as eel-grass, and abounding in slow or quiet waters of our rivers, lakes or sea-coasts. It belongs to the class Diacia, that is, the sexes are produced on different plants. The female flowers are solitary, borne on long, slender stalks, finely twisted like a spiral spring. The plant is usually found in water from two to three feet in depth, the flowers being near the root. About the time of the opening of the flower this spiral stem begins to unwind, and this elevates the flowers to the surface of the water, where they fully expand in the open air. The male flowers are produced in great numbers, on short, upright stems, issuing, as we have before said, from different plants. These flowers detach themselves about the time of the expansion of the female flowers, mounting up like little air-bubbles, and suddenly expanding when they reach the surface; then, without regard to wind or current, they float around among the female blossoms, thus bringing the stamens and pistils into immediate contact, and giving the anthers an opportunity of discharging their pollen immediately over the stigma. When impregnation is secured, the uncoiled stalk of the female plant begins again to resume its spiral form, and sinks down, as it gradually rose, to ripen its seeds at the bottom of the water.

But, why, may be asked, this singular method of fertilization? Simply to

carry out a natural law that an intelligent arrangement in the structure of plants has made a necessity, viz., cross-fertilization. There is weighty and abundant evidence that the flowers of most kinds of plants are so constructed that self-fertilization is almost an impossibility, and where plants are so fertilized the penalty of degeneration in the offspring is visibly apparent. There are many methods by which cross fertilization is secured. It is sometimes insured by the sexes being separated, and in nearly all cases by the pollen and stigma of the same flower being matured at different times. In grasses and the cereals cross-fertilization is insured by the action of the wind. Dr. Keith was the first botanist to observe this singular phenomenon. He says: "As I was accidentally looking at a field of rye-grass, situated to the south of the spot on which I then stood, the atmosphere being clear, and the wind blowing gently from the west, I was surprised to observe a thin and sudden cloud, as if of smoke-a fine dust, sweeping briskly along the surface of the grass and gradually disappearing. This cloud was soon followed by another from a different quarter of the field, and then by a third, and so on in succession for several minutes. It was a general discharge of pollen from thousands of anthers bursting at the same moment, so that no stigma ready to receive the pollen could possibly fail of being supplied, either from the anthers proper of the flowers of which it formed a part, or from those of some other flower discharging their contents into the general mass." This was written long before the fact was known that all flowers were so constructed, that self-fertilization was a rare instance instead of a general law of reproduction. Sprengel, Muller and Darwin, who have given years of unremitting study and observation on the fertilization of flowers, agree upon the general law that no organized being fertilizes itself, excepting in rare instances where the perpetuation of the species would, without it, be lost. Or, as Darwin put it, “ that nature abhors perpetual self-fertilization, and that in most plants self-fertilization is avoided by special contrivances, or even rendered impossible, or, if it does take place, it is at least injurious."

Thus far I have only alluded to the inanimate causes of cross-fertilization; I will now mention briefly the animate causes, and then make an application in which I think you will all be interested and profited so far as a knowledge of the cause of failure or of deterioration of seed may be useful. The animate agents of fertilization are, in comparatively few instances, birds; but, as a general rule, insects are the agents employed for this work, and so systematic are they in their operations, so harmoniously do they work together, that the lives of the two classes of organic beings appear a unit.

The insect is allured to the flower, and this, accordingly, appeals to its sight or smell by brilliant colors or attractive scents. These colors and these scents draw the insect to the flower from a distance; but by themselves they would be but empty gratifications, unprofitable to insect and flower alike. Something more substantial must be offered; something that will

prevent the insect from merely loitering about the flower in idle satisfaction, and that will induce it to probe to the recesses of the blossoms, and, in so doing, to transfer the pollen of one flower to the stigma of another. This further allurement is addressed so the palate, and though in some cases it is nothing more than the pollen itself, in most it is supplied by the secretion of a sweet fluid, the so-called nectar.

Now, Nature, who at first sight often appears a prodigal, is always found on closer examination to be the most rigid of economists. If no insects are to be allured, she gives, as we have seen, no nectar; she cuts off the bright petals and suppresses the attractive odors. Nor even when a bait is wanted will she give it one minute sooner than is necessary. The brilliancy, the scent and the nectar are only furnished when the flower is ready for its guests, and requires their presence; just as a thrifty housewife lights her candles when the first guest is at the door. The miniature bud has no such attractions. Still more, even when the flower is mature, when its pollen is ready for transference, or its stigma for fecundation, when all the allurements are consequently displayed, and insects invited to the feast, she still shows her economy. Guests might come who were not of sufficient importance, and the banquet be wasted on them; for it is only when insects have a certain shape, size or weight that she requires their visits, and can use them profitably for her purposes. She requires, moreover, that they shall make their visits by the main portal, which she has specially adapted to suit both their and her own requirements. All insignificant and unremunerative visitors, all such, moreover, as would creep in by a back entrance, must be kept out. Insects of all denominations are but transient visitors, their lives are short; many, if not the most, of the species live no longer than the flower upon which they feed. Each and every species or genera of plants is furnished with an insect for the purposes of cross fertilization, and when the work is accomplished, the life of the plant is wrapped up in the seed and the life of the insect in the chrysalis, where it will remain until required again for the purposes which its creation was intended to accomplish.

There is a stronger and closer analogy between the sexual organs of animals and plants, which manifests itself in the plant at the time of flowering, to which I will now call your attention. This is the evolution of heat in the female organ of the plant when it is ready for impregnation.

This phenomenon is supposed to exhibit itself in all flowers; there are but few, however, so arranged that any test can be made to satisfactorily demonstrate the fact. The discovery of this singular phenomenon, like many others, was purely accidental. It was first noticed by that celebrated botanist, Brongniart, in examining a flower of the Colocasia odorata, a tropical plant grown exclusively in our green-houses for the beauty of its foliage. This plant, he said, at the time of flowering presented an increase of temperature that might almost be compared to an attack of daily fever. These attacks were repeated for six following days with a considerable intensity, and almost at the same hour, commencing at three and lasting until six in