The white day or Japan lily (Funkia japonica) (Fig. 56) opens about sundown, giving forth an alluring sweetness. I have never seen a winged insect accept this seductive invitation, but as the long blossom-tubes are sometimes followed by shining, green seed-vessels, it is evident that the day lily occasionally receives a visitor, who comes under cover of night. A flower-tube so long as this can be drained only by an insect with a very long proboscis. Such insects are large and conspicuous, and if they flew by day would be speedily "nabbed" by birds, collectors, or small boys. Like Leander, they must pay their addresses by night for life's sweet sake.
Fig. 56. - Day or "Japan" lilies (Funkia Japonica).
So the deepest-throated flowers are almost all nocturnal. The jasmine, the tuberose, and ste-phanotis, which keep their nectar in very long and slender tubes, blow at evening, and give their fragrance to the night. The Yucca Filamentosa, familiarly known as "Adam's needle and thread," is another familiar garden night-flower (Fig. 57).
By day its greenish-white flowers are bell-shaped and odorless; and if the twilight be cold or rainy its coming makes little difference in their aspect. But on a clear, sultry evening, soon after sunset, the yucca shows a marked change. Its blossoms open widely, spreading into great six-pointed stars, and breathe forth a very penetrating and characteristic odor.
As morning breaks the blossoms lose the starlike form, and sunshine finds them scentless bells once more, dangling in the lassitude consequent upon a night of alert, and probably futile, wakefulness.
For this yucca is brought to our gardens from the South, and is accustomed to have its pollen fetched and carried by subtropical night-rovers. Few native nocturnal moths are able to sip its sweets or transfer its pollen; and if, during its brief term of beauty, a spell of cold rain discourages insect-rovers, the whole creamy spire of flowers may bloom and fade without setting a single seed.
But in fine, warm summer evenings they are sometimes visited by the small moth which fertilizes the wild yuccas of the Georgia coast.
The mode of procedure of this little wanderer is peculiar. She is a mother moth, seeking shelter and maintenance for a young family, and she has no aim except the welfare of her future offspring.
But in attending to her own affairs, she, incidentally, takes charge of the yucca's affairs also. The coming family are to be housed in the seed-vessel of the plant, and nourished on its young seeds.
But the yucca's pistil and stamens are so situated, with regard to each other, that pollen can scarcely reach the stigma without the aid of insect ministrations.
Fig. 57. - "Adam's needle and thread " (Yucca filamentosa).
And the mother-moth seems to understand that unless the pistil is touched by pollen from the anthers there will be neither seed-vessel nor seed. She first bores the ovary in several places, and in each hole she deposits an egg. Then she collects load after load of pollen from the anthers, gathering it up by means of a long, coiling organ, which seems to have been given her for this special purpose. She thrusts most of this pollen into the holes with the eggs, so that it makes warm and dry beds for the grubs that are to be. And, guided by a marvellous instinct, she also places some of it on the stigma of the flower. So as the grubs develop in the ovary, the seeds which serve as their food develop also, and with them so many other seeds that the perpetuation of the yucca family is ensured.
"When the grub is full grown," says Muller, "it bores a hole through the capsule, lowers itself to the ground by a thread, digs its way a few inches into the soil and spins a cocoon, in which it spends autumn, winter, and spring".
In its native haunts it passes into the pupa stage about fourteen days before the Georgia yucca (Yucca recurvifolia) begins to bloom, and emerges from its temporary tomb as the flowers expand. But it is probable that our average winters are too severe for a transplanted southern family, and that most of the Pronuba yuccasella larvae in our gardens freeze with the freezing soil, and thus perish untimely. Some few, however, survive the winter evidently and make use of the yucca blossoms as their mother did before them, for in most seasons we will find a few capsules full-grown and symmetrically formed, but with holes in them.
And so wounded and marred, the flowers have fulfilled the purpose of their lives, and attained a development which they might not otherwise have reached.
Occasionally one finds a perfectly-developed capsule which is not pierced, showing that the yucca receives visits, few and far between, from some nocturnal guest which fertilizes the blossoms without marring them. But in many seasons no efficient callers come to the flowers and no capsules form at all.
Many of the white Japan lilies are likewise disappointed, so large a proportion of them, in fact, that one season, when my garden yielded twenty large heads of bloom, each bearing many flowers, only eight capsules formed.
But the night-flowers which blow in the fields, even when they are of foreign descent, have near kin among the aborigines of the soil. So each has its insect attendant, faithful to the family, time out of mind, and their sweetness is not wasted, nor does Nature's purpose for them fail.