tissue, soon constitutes itself an accessory but important part of the plant, which is known by the name of albumen.

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We have now rapidly set forth the functions of the pollen and the ovule in the great phenomenon which secures the perpetuity of the species; but in this rapid glance at some of the most secret mysteries of vegetable fecundation, we have stated the facts without occupying ourselves with any of the external circumstances, that is to say, the influences acting from without, which prepare for it, and which determine and favour it. We now enter into Some details on this subject, and of some of the phenomena accompanying fecundation.:

In a great number of hermaphrodite flowers, the stamens at the period of fecundation elevate their anthers higher than the stigma; so that the pollen falls naturally upon it at the moment of the opening of the anthers. In other flowers, the stamens carry their anthers lower than the stigma, but the flower is habitually inclined or suspended, as in the Fuchsia; the deposition of the pollen on the stigma is then made without any obstacle.

When the stamens and pistils are not close to one another, nature sets the necessary means to work to promote their near ’pproach. Thus, we observe in different plants some very curious and varied movements in the stamens, at the period of fecundation. In the Nettle, the Mulberry, and the Pellitory, for instance, the

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filaments of the stamens are bent backwards on themselves, under the pressure of the floral envelope; but as soon as full bloom takes place the filaments unroll and the pollen is projected to a distance of thirty or forty inches or more. This movement is simply the result of the elasticity of the organs. In the Rue, at the moment of fecundation, each of the numerous stamens constituting the andraczeum, bends itself over the stigma, deposits the pollen there, and resumes its former position. Here is an individual and really spontaneous movement. In the Passion-flower the styles are at first erect, but at the moment of the opening of the anthers, they are observed to curve downwards, and lower themselves towards the stamens, and: then to rise up and resume their former position.

In the flower of the Barberry, if a stamen is touched with the point of a pin, it is brought close to the pistil by a sudden movement, and then, in a little time, resumes its former position;and this it will do again if fresh irritation is produced. A phenomenon of irritability is shown here, which does not exist in the other cases just specified. The hairs which cover the styles of the Campanula show a very singular property. They fold back on themselves, like the finger of a glove, the end of which is pushed inwards, and they draw with them into this retreat the grains of pollen, the fall of which they thus determine. In a pretty little plant of New Holland, known under the name Leschenanthia, the stigma is in the form of a cup, and it is edged with rather long hairs. At the moment of the anthers opening; part of the pollen falls into the cup of the stigma, which contracts in order to grasp them, whilst the hairs approach each other so 48 to prevent the exit of the fertilising dust.

In the facts we have just pointed out, the organs themselves act to produce the fecundation of the flower. But this physiological action is often facilitated by the concurrence of exterior agents. The wind has power to transport the pollen to a certain distance, and thus favours the fecundation of the flowers in mon@ci0us, diecious, or polygamous plants. Insects, while flitting from flower to flower, often become the active instruments of vegetable fecundation.

In the Orchidacee, in which the structure of the pollen is very peculiar, the intervention of insects appears favourable, but not indispensable, to fecundation.

When the doctrine of sexual organs in vegetables was first made public by Linnzus, it was disputed by many. Conrad Sprengel, a patient observer, watched during many long hours for the instant when an insect, settling on a flower, should suck out its sweet-smelling juices and deposit the pollen grains on the stigma of the flower. Sprengel succeeded in this way in verifying a natural fact, interesting without doubt, but it was no argument against the doctrine of Linnzeus; nor did the work he published in which all the arguments against the sexual system in plants were reproduced, at all change the current of the new ideas.

In certain climates the Aumming-birds are useful auxiliaries in the fecundation of flowers. The hand of man, also, frequently intervenes in practising artificial fecundation—bringing in this way the most convincing of all arguments in favour of the doctrine.

We may instance as an example the fecundation of the Date-tree, which is practised in Algeria and all over the East, as related by a botanist who has studied the subject on the spot:—“ Towards the month of April,’ says M. Cosson, “the Date-tree begins to flower, and then artificial fecundation is practised extensively. The male spathes are opened at the time when a sort of crackling is produced under the finger, which indicates that the pollen of the flowers in the cluster is sufficiently developed, yet has not escaped from the anthers; the cluster is then divided into fragments, each containing seven or eight blooms. Having placed the fragments in the hood of his durnous, the workman climbs with marvellous agility to the summit of the female tree, supporting himself by a loop of cord passed round his loins, and at the same time round the trunk of the tree. He glides with great address between the stalks of the leaves, the strong and sharp thorns of which render the operation rather dangerous; and having split open the spathe with a knife, he slips in one of the fragments, which he interlaces with the branches of the female cluster, the fecundation of which is now made certain.”

Another phenomenon sometimes exhibits itself at the time of flowering,which bears an intimate relation to fecundation; this is the

production of heat. M. Ad. Brongniart has made some experiments on this subject which have become famous. At the time of opening, the flowers of the sweet-smelling Colocasia presented to this observer 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; for it was between three and six in the afternoon that this increase of temperature reached its maximum. Analogous phenomena have been noticed at the time of fecundation in the flowers of our common Arum (Arwm vulgare), of the splendid Victoria Regia, the Magnolia, and some other plants.

It is impossible to conclude our remarks on the fecundation of plants without instancing the aquatic plant known as Vallisneria spiralis, which has long been the admiration of naturalists, while poets have sung its praises. The Vallisneria is a dixcious plant; that is, it has male and female individuals existing separately, in the tranquil waters of some countries in central Europe, pril-cipally France and Italy (Fig. 271). In the female plant the peduncle of the flower is very long, having the form of a spiral twisted thread-like filament. A few days before fecundation the © spiral turns untwist themselves, and the peduncle lengthens, until the female flower terminating it reaches the surface of the water, and floats on its surface. The male plant presents, on the contrary, a.very short peduncle, which is not capable of any extension; it bears a multitude of little flowers, provided with stamens only, and enveloped by a closed transparent spathe. At the time of full bloom the spathe is torn, the peduncle of the male flower severs itself towards its upper part, and the flowers separated from the stalk rise: all shut up, like very small white pearls; they float on the surface of the water, and proceed to open near the female flower, which seems to wait for them. When fecundation has been effected, the peduncle of the female flower contracts; it brings together its spiral turns, and carries its ovary to the bottom of the water, in order to ripen its seed.;

This is a phenomenon which has always excited the just adml-ration of naturalists and observers of every class. I was initiated into the first elements of natural science, at the Lyceum of my native town by M. Joly, now professor of the Faculty of Science

at Toulouse, a young professor then, who excelled in inspiring his pupils with a taste for this sort of study. The wonderful inci-dents attending the nuptials of the Vallisneria spiralis, or still more the marvellous evolutions of the Nautilus floating on the sea, or disappearing in its depths at its own pleasure, were the favourite texts for the discourses of M. Joly during our botanical and geological excursions round Montpelier, in the flower-decked wood of La Valette, or on the volcanic summit of Monferier. Thirty years have elapsed since those happy youthful days, and the recollection is just as vivid, just as present to my mind as if I still heard the burning words of our then young teacher ringing in my ears, telling us, under our radiant skies, all about the wonders of nature, and the power of God.

GERMINATION.

In order that a seed should germinate, three conditions are requisite—heat, air, and moisture; temperature, varying in different species, must not be much less than 10° or 15° (centigrade), and it must not reach higher than 40° or 45°.

Moisture penetrating the seed beneath the ground softens it, swells all its parts, and allows their intimate evolution.:

Air is also as indispensable to the germination of seeds as it is to animal life. Seeds which are buried too deeply in the ground, and are thus cut off from the air, will never germinate.

What, then, is the important part that atmospheric air performs in the act of germination? It is just the same as that which it fulfils in the respiration of animals. Air acts on the seed by means of its oxygen. The germinating seed, like the animal, breathes out carbonic acid. It takes up carbon into its Own substance, and the carbon combines with the oxygen of the air to form carbonic acid; but from the instant when, by the progress of germination, the young plant has produced small green leaves, the chemical pkenomenon is, so to speak, reversed. In the daytime, and under the influence of light, the young plant absorbs carbonic acid from the air, and replaces it with oxygen; its respi- _ ration takes place just as we stated when speaking of this physiological function in the green-coloured portion of vegetables. )

We will now follow the series of phenomena presented to the observer by the germination of a seed.

The first apparent effect of germination is the swelling of the seed, and the softening of the coverings that envelope it. If the seed is enclosed in albumen, the embryo, which is in contact with the albumen, either over its whole surface, or the greater part of it, absorbs the nutritive matters which it contains, and increases in size in the same proportion as the albumen gets less, being developed at the expense of the substance stored up for this end by a provident nature. If the seed is destitute of albumen, and the embryo at the time of dissemination fills up the whole cavity of the seed, then the cotyledons—which are farinaceous in the Pea, or fleshy in the Nut or Cole-seed—which form the greater portion of the embryonic mass, will perform the part of albumen, as regards the rest of the embryo. Fig. 283 represents the first effort of germination in the Bean, a plant not provided with albumen. It was long a mystery how the starch of which the albumen of Wheat is almost entirely constituted, can be absorbed by the young embryo, since the radicles of plants absorb soluble matters only, and starch is completely in cold water. But insoluble has been discovery the interesting lately made, that the insoluble starch becomes soluble under the

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