efficiency of their mechanism. First, it is necessary that carrying agents should be employed to convey the pollen; and we find that of these there are two classes the wind and various insects. These are Flora's carriers, whom she intrusts with a most delicate mission, and that they perform it well we may see by the lavish manner in which the fields, the lanes, and woods are adorned with living gems.

Flowers which are fertilised by the wind are never conspicuously coloured; and here we find the reason why flowers are brightly coloured. If we observe an organ in any plant or animal which is of no apparent use to it, we may be sure that it has had a use in the past, among the ancestors of the species, for Nature does not provide organs or adornments unnecessarily. However beautiful in appearance may be a flower, we shall find on closer acquaintance that its beauty is not merely to gratify our sense of the beautiful, but to serve a useful purpose in the economy of Nature, and with special reference to the species possessing it. Thus there is not a single windfertilised flower that is highly coloured, because its colouring would be unnecessary; on the contrary, nearly all insect-fertilised † flowers are brightly and conspicuously coloured. Taken in conjunction with other facts which we shall adduce, the reason for this is sufficiently obvious-the bright hues are to attract insects to the flower. Again, wind-fertilised flowers produce vast quantities of pollen; insect-fertilised flowers produce very little. In the first case, the pollen being carried, as in the fir, from tree to tree, * Anemophilous. + Entomophilous.

*

great quantities must be lost in transit by being blown in a direction where there are no other trees of the species, or by falling to the ground. Therefore it is necessary that very large quantities should be produced to ensure that the small amount requisite for fertilisation should reach its proper destination. But in flowers fertilised by insects no such risk is run, therefore only a small amount of pollen is produced.

Then, too, we find a marked difference in the stigma of a wind-fertilised as compared with an insect-fertilised plant, which will be best explained by reference to these diagrams. Fig. 45 shows the stigmas of Wheat and Hop, which are anemophilous; fig. 46 those of the Primrose and Heath, which are entomophilous. In fig. 45 it will be observed the

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FIG. 45.

a

b

FIG. 46.

stigmas are more branched and hairy, the object, of course, being to offer a larger surface to catch the wind-borne pollen grains. In fig. 46, of insect-fertilised plants, the stigmas are of a simpler form. We have remarked that the colours of flowers are for the attraction of insects, and to prove this we must show that insects are sensible to colour. The experiments of Sir John Lubbock, who has added so much to our knowledge of insects, show this conclu

sively. He says: "That bees are attracted by, and can distinguish, colours was no doubt a just inference from the observations on their relations to flowers; but I am not cognisant of any direct evidence on the subject. I thought it, therefore, worth while to make some experiments; and a selection from them will be recorded in the forthcoming volume of 'Journal of the Linnean Society.' I placed slips of glass with honey on paper of various colours, accustoming different bees to visit special colours, and when they had made a few visits to honey on paper of a particular colour, I found that if the papers were transposed the bees followed the colours."*

If bees in a garden are watched, they will be seen to confine their attention to one particular species, though they have been observed to be incapable of distinguishing between certain closely-related species, though this may indicate that they are not true species, but only varieties.

Most flowers which have an irregular corolla-that is, with the petals unequal in size and form—are, according to Mr. Darwin, insect-fertilised; and he says it is very probable that those species which are habitually self-fertilised receive fresh vigour from an occasional cross. Sir John Lubbock, in his charming book, has entered fully into the question as affecting our native wild plants, and has given examples from most of the natural orders and families. It is impossible in the small space at present at our disposal to do more than give a few of the most striking illustrations. Why should the bees and other insects go to

* Wild Flowers in Relation to Insects, p. 12.

all this trouble? What benefit do they derive from the transaction? These are questions which will probably have occurred ere this to the reader's mind. They are easily answered by the facts-so, too, are many others in connection with flowers that used to puzzle people to explain satisfactorily. Why are flowers provided with honey and sweet perfumes? Why are flowers highly coloured? Why do flowers "go to sleep"-i.e., close their petals-at night, and in rainy weather?

These and many other questions are answered by modern science satisfactorily. The insects are attracted from a distance by the perfume of the flower; they are shown the exact spot by the colour of the corolla; and they evidently are aware, from inherited instinct, that sweet odours and bright hues are the outward signs of a store of honey. The insects find their reward in the honey; the honey, then, is only a bait to induce the insect to visit the flower, and detach and carry the pollen. Flowers which are fertilised by bees or butterflies, which fly by day, close their petals at night, for it would not be to their advantage to have their honey stolen by night-flying moths, who cannot fertilise them. On the contrary, night-flowering plants keep the petals closed during the day, because they are fertilised by moths; and to render them conspicuous they are light in colour. Thus, the White Campion, which flowers at night, is of a silver-white hue, and the light-yellow Evening Primrose has the additional assistance of a very strong sweet perfume. Flowers, too, close in rainy weather to protect their honey. Many flowers which

depend upon the honey for their fertilisation are specially constructed to protect it. The honey is generally so situated in flowers that to get at it the insect is bound to push itself against the anthers, and when it retires it takes away some of the pollen on its body or head. The stigmas and anthers are usually so placed that on visiting the next flower the pollen on the insect comes into contact with the stigma, and is detached.

H

A

St

In some cases the stamens and stigmas do not ripen at the same time, so that it is impossible for the plant to be self-fertilised. This is the case with the common Arum, in which the stigmas come to maturity before the anthers. Any one acquainted with the flowers of this plant -and few persons are not-will understand that it is impossible for the pollen to be blown out of the flower after it has been shed by the anthers; and though, from their being placed above the stigmas, it would seem an easy matter for selffertilisation to take place, this is prevented by the stigmas maturing before the pollen is ripe; so that if it is to be fertilised at all, it must be by pollen being brought from a plant which has flowered a little earlier, and in which the stigmas have passed maturity. Just above the band of anthers (A) are a number of hairs (H) pointing downwards. Small insects in quest of honey easily pass these hairs and reach the bottom, but on wishing to return, these same hairs, from their direction, form an effectual barrier, and the insects remain

FIG. 47.