The Evening Primrose
THE summer which is allowed to pass without a visit to the twilight haunt of the evening primrose, perhaps at your very door, is an opportunity missed. Night after night for weeks it breathes its fragrant invitation as its luminous blooms flash out one by one from the clusters of buds in the gloom, as though in eager response to the touch of some wandering sprite, until the darkness is lit up with their luminous galaxy—that beautiful episode of blossom-consciousness and hope so picturesquely described by Keats:
"A tuft of evening primroses
O'er which the wind may hover till it dozes,
O'er which it well might take a pleasant sleep,
But that 'tis ever startled by the leap
Of buds into ripe flowers."
Nor is it necessary to brave the night air to witness this sudden transformation. A cluster of the flowers placed in a vase beneath an evening lamp will reveal the episode, though robbed of the poetic attribute of their natural sombre environment and the murmuring response of the twilight moth, a companion to which its form, its color, and its breath of perfume and impulsive greeting are but the expression of a beautiful divine affinity.
Then there is that pretty daylight mystery of the faded, drooping bells of last night's impulsive blossoms, each perhaps tenanted by the tiny, faithful moth which first welcomed its open twilight chalice, and which now has crept close within its wilted cup, the yellow tips of its protruding wings simulating the fading petals. And again, a few weeks later, with what surprise do we discover that these long columns of green seed-pods are not always what they seem, but are intermingled with or supplanted by smooth, green caterpillars which exactly resemble them in size and general shape, the progeny of our tiny pink and yellow moth now feeding on the young seed-pods! Verily even a vireo or worm-eating warbler, who is supposed to know a green caterpillar when he sees one, might perch among these without a suspicion, except perhaps at the tickling of its feet by the rudely touched victim.
But these are not all the interesting features of the evening primrose. It has still another curious secret, which has doubtless puzzled many a country stroller, and which is suggested in the following inquiry from a rural correspondent:
"I read in 'Harper's Young People' your piece about the evening primrose, and found the little moth and the catterpilers, what I never seen before; but they is one thing what you never tole us about yit. Why is it that the buds on so meny evening primroses swell up so big and never open? Some of them has holes into them, but I never seen nothing cum out."
This same question must have been mentally propounded by many observers who have noted this singular peculiarity of the buds—two sorts of buds, one of them long and slender, and with a longer tube; the other short and stout, with no tube at all—both of which are shown in proper proportion in my illustration. It is well to contrast their outward form, and to note wherein they differ. In the normal or longer bud the tube is slender, and extended to a length of an inch or more, while in the shorter specimen this portion is reduced to about a fifth or sixth of that length, while the corolla enclosed within its sepals is much shortened and swollen.
The difference in the shape and development of these two buds is a most interesting study, as bearing upon the conscious intention of the flower as an embodiment of a divine companion to an insect. What is the intention involved in the construction and habit of this flower? Why this long tube? Why does it await the twilight to burst into bloom?
In the new botany of Darwin flowers must be considered as embodiments of welcome to insects. Long ago it was discovered that the powdery pollen of a flower must reach the stigma of the flower in order to produce seed. It was formerly supposed that this was naturally accomplished by the stamens shedding this pollen directly upon the stigma, but this was later shown to be impossible in most flowers, the anthers containing the pollen being so placed that they could not thus convey the pollen. This fact was first noted by Sprengel in 1787, who was the first to discover that the flower, with its color, perfume, and honey, was really designed to attract insects, and that only by their unconscious aid could the pollen be thus carried to the stigma. But Sprengel had supposed that the intention of the blossom was the reception of its own pollen, a fact which was again soon seen to be impossible, as the stigmas of many flowers are closed when their own pollen is being shed. It remained for Darwin seventy years later to interpret the problem. Insects were intentionally attracted to the flower; but the pollen with which their bodies thus became dusted was designed to be carried to the stigmas of another flower, showing cross-fertilization to be the intention in nearly all blossoms.
The endless shapes of flowers were shown by Darwin to have reference to certain insects upon whom the flower depended for the transfer of its pollen. What are we to infer from the shape of our evening primrose? Its tube is long and slender, and the nectar is secreted at its farthest extremity. Only a tongue an inch or so in length could reach it. What insects have tongues of this length? Moths and butterflies. The primrose blooms at night, when butterflies are asleep, and is thus clearly adapted to moths. The flower opens; its stigma is closed; the projecting stamens scatter the loose pollen upon the moth as it sips close at the blossom's throat, and as it flies from flower to flower it conveys it to other blossoms whose stigmas are matured. The expression of the normal bud is thus one of affinity and hope.
Our friend just quoted mentions having seen "holes" on the other swollen buds, and there is certain to be a hole in every one of them at its maturity. But let us select one which is as yet entire. If with a sharp knife-point we cut gently through its walls, we disclose the curious secret of its abnormal shape—"the worm i' the bud," as shown in my accompanying sketch—and what an eloquent story of blighted hopes its interior condition reveals! This tiny whitish caterpillar which we disclose in the petal dungeon has been a prisoner since its birth, during the early growth of the bud. One by one the stamens and also the stigma have been devoured for food, until the mere vestiges of them now remain. With no stamens to bequeath pollen, and no stigma to welcome other pollen, what need to open? What need to elongate a corolla tube for the tongue of a moth whose visit could render no functional service? So thus our blighted buds refuse to open, where blooming would be but a mockery. This tiny caterpillar has a host of evening primrose blossoms laid to his door. When full grown he is nearly a third of an inch in length, at which time he concludes to leave his life-long abode, which explains the "hole" through the base of the bud. If we gather a few of these buds and place them in a small box, we may observe the remaining life history of the insect. After creeping from its petal home it immediately spins a delicate white silken cocoon, and within a day or so changes to a chrysalis. At the expiration of about a fortnight, as we open the box, we are apt to liberate one or more tiny gray moths, which upon examination we are bound to confess are a poor recompense for the blossom for which they are the substitute.
This little moth is shown very much enlarged in the accompanying illustration. Its upper wings are variously mottled with gray and light brown, and thickly fringed at their tips, while the two lower wings are like individual feathers, fringed on both sides of a narrow central.
These and other characters ally the insect with the great group known as the Tineidæ, of which the common clothes moth is a notorious example.
