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THE ORIGIN OF FLOWERS.
their contents. Malva rotundifolia can be, and often is, sucked by bees from the outside, in which case the flower derives no advantage from the visit of the insect. In Medicago sativa, also, insects can suck the honey without effecting fertilisation, and the same flower continues to secrete honey after fertilisation has taken place, and when, apparently, it can longer be of any use. Fritz Müller has observed that though Posoqueria fragrans is exclusively fertilised by night-flying insects, many of the flowers open in the day, and consequently remain sterile. It is of course possible that these cases may be explained away; nevertheless, as both insects and flowers are continually altering in their structure, and in their geographical distribution, we should naturally expect to find such instances. Water continually tends to find its own level ; animals and plants as constantly tend to adapt themselves to their conditions. For it is obvious that any blossom which differed from the form and size best adapted to secure the due transference of the pollen would be less likely to be fertilised than others; while on the other hand, those richest in honey, sweetest, and most conspicuous, would most surely attract the attention and secure the visits of insects; and thus, just as our gardeners, by selecting seed from the most beautiful varieties, have done so much to adorn our gardens, so have insects, by fertilising the largest and most brilliant flowers, contributed unconsciously, but not less effectually, to the beauty of our woods and fields.1
1 I have treated the suhject of these chapters at greater length in a little book on Flowers and Insects, forming one of the present series.
FRUITS and Secds, though not generally so conspicuous as flowers, are not less interesting.
In considering them, it is fortunately not necessary to use many technical terms, though it is impossible
STRUCTURE OF SEED.
to avoid them altogether. In order to understand the structure of the seed, we must commence with the flower, to which the seed owes its origin. Now I have already mentioned, but it may be convenient to repeat here, if you take such a flower as, saya Geranium, you will find that it consists of the following parts: Firstly, there is a whorl of green leaves, known as the sepals, and together forming the calyx secondly, a whorl of coloured leaves, or petals, generally forming the most conspicuous part of the flower, and called the corolla ; thirdly, a whorl of organs more or less like pins, which are called stamens, in the heads, or anthers of which, the pollen is produced. These anthers are in reality, as Goethe showed, modified leaves; in the so-called double flowers, as, for instance, in our garden roses, they are developed into coloured leaves like those of the corolla, and monstrous flowers are not unfrequently met with, in which the stamens are green leaves, more or less resembling the ordinary leaves of the plant. Lastly, in the centre of the flower is the pistil, which also is theoretically to be considered as constituted of one or more leaves, each of which is folded on itself, and called a carpel. Sometimes there is only one carpel. Generally the carpels have so completely lost the appearance of leaves, that this explanation of their true nature requires a considerable amount of faith, though in others, as for instance in the Columbine (Aquilegia), the original leaf-form can still be traced. The base of the pistil is the ovary, composed, as I have just inentioned, of one or more carpels, in which the seeds are developed. I need hardly say that many
PROTECTION OF SEEDS.
so-called seeds are really fruits ; that is to say, they are seeds with more or less complex envelopes.
We all know that seeds and fruits differ greatly in different species. Some are large, some small; some are sweet, some bitter ; some are brightly coloured ; some are good to eat, some poisonous ; some spherical, some winged, some covered with bristles, some with hairs; some are smooth, some very sticky.
We may be sure that there are good reasons for these differences. In the case of flowers inuch light has been thrown on their various interesting peculiarities by the researches of Sprengel, Darwin, Müller, and other naturalists. As regards seeds also, besides Gartner's great work, Hildebrand, Krause, Steinbrinck, Kerner, Grant Allen, Wallace, Darwin, and others, have published valuable researches, especially with reference to the hairs and hooks with which so many seeds are provided, and the other means of dispersion they possess. Nobbe also has contributed an important work on seeds, principally from an agricultural point of view, but the subject as a whole offers a most promising field for investigation. It is rather with a view of suggesting this branch of science to you, than of attempting to supply the want myself, that I now propose to call your attention to it. In doing so I must, in the first place, express my acknowledgments to Mr. Baker, Mr. Carruthers, Mr. Hemsley, and especially to Mr. Thiselton Dyer and Sir Joseph Hooker, for their kind and most valuable assistance.
It is said that one of our best botanists once observed to another that he never could understand what was the use of the teeth on the capsules of mosses. “Oh,"
EDIBLE FRUITS AND SEEDS.
replied his friend, “I see no difficulty in that, because if it were not for the teeth, how could we distinguish the species ?”
We may, however, no doubt, safely consider that the peculiarities of seeds have reference to the plant itself, and not to the convenience of botanists.
In the first place, then, during growth, seeds in many cases require protection. This is especially the case with those of an albuminous character. It is curious that so many of those which are luscious when ripe, as the Peach, Strawberry, Cherry, Apple, &c., are stringy, and almost inedible, till ripe. Moreover, in these cases, the fleshy portion is not the seed itself, but only the envelope, so that even if the sweet part is eaten the seed itself remains uninjured.
On the other hand, such seeds as the Hazel, Beech, Spanish Chestnut, and innumerable others, are protected by a thick, impervious shell, which is especially developed in many Proteaceæ, the Brazil-nut, the socalled Monkey-pot, the Cocoa-nut, and other palms.
In other cases the envelopes protect the seeds, not only by their thickness and toughness, but also by their bitter taste, as, for instance, in the Walnut. The genus Mucuna, one of the Leguminosæ, is remarkable in having the pods covered with stinging hairs.
In many cases the calyx, which is closed when the flower is in bud, opens when the flower expands, and then after the petals have fallen closes again until the seeds are ripe, when it opens for the second time. This is, for instance, the case with the common Herb Robert (Geranium robertianum). In Atractylis cancellata, a South European plant, allied to the thistles,