Page:Popular Science Monthly Volume 31.djvu/98

88 drops its two sepals as they open, leaving the delicate, pure, white petals and the April insects to succeed as best they can in the work of cross-fertilization. Just what kinds of bees, or bugs, or beetles stand ready to rob each opening flower of its sticky pollen, I am not prepared to say. It is true that the blood-root has few competitors, at this time of year, for the employment of the insect tribes. Its petals are large, and doubtless catch the watchful eyes of the hungry insects at long range. The plant and the insect work together, each selfishly, yet each successfully. The mutual adaptation existing between some flowers, as those of many orchids and their attendant insects, is so complete that neither the plants nor the insects could well exist without one another. Some plants are absolutely dependent upon certain insects for the transfer of their pollen, while these same insects could not subsist without the flowers from which to extract their daily food. In our little blood-root, we do not believe such a thorough dependence exists. If insects do not bring more potent pollen from some other flower, that of its own, falling upon the stigma close by, will suffice.

On April 13th two species were found in flower, and between them there are seemingly wider differences of structure than were pointed out in the last two. The white elm (Ulmus Americana, L.) is a large tree, famous for its grace and beauty in the hands of the landscape gardener. The Stellaria media (Smith) is the common chickweed, so abundant around dwellings in every part of the world. The stately elm is an American species, as its botanical name indicates, while the chickweed is one of a large class of plants which have come to us unbidden, and frequently unwelcomed, from beyond the sea. Its greatest economic value seems to be as a salad-plant for canary and other imprisoned birds. This little, insignificant herb delights in cold, shady soil, and frequently opens its blossoms beneath, or when surrounded by, drifts of snow. There seems to be no good foundation for this haste, as the plant continues in bloom during nearly its whole lifetime of a year or more. It also seems as if it would be just as well to delay flowering until insects are more numerous, at which times the blossoms secrete so much honey that the drops may be seen without a hand-lens. Among other insects, the prolific aphides (plant-lice) and the ubiquitous house-fly (Musca domestica, L.) are attendant upon the unobtrusive chickweed-flowers. The blossoms of the elm are also small, but depend upon the winds for transfer of their pollen. The leaves do not unfold until the flowers are past, and in this circumstance we may see an instance of the working of the law of adaptation. The foliage might interfere with the easy movement of the dry, dusty pollen from one tree or branch to another. Students of plant-life are always pleased to observe that adaptations for cross-fertilization are worked out along very many lines. The elm offers an instance in which there is a seeming confusion in the floral type. Botanists say the elms are polygamous, which only means that some flowers are