It not unfrequently happens that a flower possesses stamens and no pistil, or a pistil and no stamens. Flowers of this kind are technically termed diœcious (Greek _dis_, twice, and _oikia_ or _oikos_, place of abode), if the male and female flowers are on different plants. The flowers of such plants as oaks and birches are male and female, but are borne on the same plant, hence termed monœcious (Greek _monos_, single). The flowers that contain stamens only are called male flowers, and those containing pistils only are named female flowers. The oaks and birches, as has been stated, have both the male and female flowers on the same plant, though in other cases the male flower is borne on one plant and the female flower on another. In cases like these the wind carries the pollen from one plant to another. In wind-fertilized flowers the flower is usually produced prior to the foliage leaves, or at least before the plant is crowded with leaves. These plants produce an immense amount of pollen. Besides the transference of pollen by the agency of the wind, insect agency plays a very important part. These insect-fertilized plants are much more conspicuous than those fertilized by the wind. There are numerous natural contrivances in plants to prevent self-fertilization, as this process of self-fertilization is far less effective in producing seeds than when the ovules are fertilized by pollen from another plant of the same species. In some plants the stigma is mature before the anther, and in such a case the pollen must be brought from a flower that has bloomed a little earlier than itself. FLORA OF THE EARLY MESOZOIC --SIR J. WILLIAM DAWSON Great physical changes occurred at the close of the Carboniferous age. The thick beds of sediment that had been accumulating in long lines along the primitive continents had weighed down the earth’s crust. Slow subsidence had been proceeding from this cause in the coal-formation period, and at its close vast wrinklings occurred, only surpassed by those of the old Laurentian time. Hence in the Appalachian region of America we have the Carboniferous beds thrown into abrupt folds, their shales converted into hard slates, their sandstones into quartzite and their coals into anthracite, and all this before the deposition of the Triassic Red Sandstones which constitute the earliest deposit of the great succeeding Mesozoic period. In like manner the coal-fields of Wales and elsewhere in western Europe have suffered similar treatment, and apparently at the same time.