Page:Popular Science Monthly Volume 45.djvu/30

18 for centuries to come. Every one with the least knowledge of the vegetable world knows that the great majority of flowering plants have the stamens and pistils in the same blossom, although Nature generally devises some method of preventing self-pollination. Many species, however, bear the pistillate blossoms on one plant or part of the plant, and the staminate blossoms on another plant or part of the plant, relying on insects or the wind to carry the pollen from the latter to the former. But occasionally there occurs a species whose flowers are neither wholly one nor the other, being in a transition stage between the two. In this category we find the mayflower.

The examination of the structure of a dozen bunches of arbutus blossoms reveals a great variation in the relative conditions and positions of the stamens and pistils. In some specimens the anthers are completely abortive; in others only partially so; and in others in good condition, well filled with pollen grains. Two types of stigmas are also present: in some specimens the stigmas as a whole are broad and more or less flattened—spread out, so to speak—projecting at right angles to the style with the upper surface moist and glutinous; in others the stigmas are crowded into less space and project very little horizontally; they are drier and less glutinous, and evidently in a partially abortive condition. The perfect stigmas are usually associated with abortive anthers, and vice versa, so that many of the plants are already diœcious.

If the flowers are examined with reference to the length of the styles and filaments of the pistils and stamens, great variations will also be found. In some the stigmas are perfect and reach the mouth of the corolla; no anthers, and only rudiments of filaments are present. The variations I found on Blueberry Hill at Hanover, New Hampshire, may be epitomized as follows:

1. Stigmas perfect, reaching the mouth of the corolla; no anthers, and only rudiments of filaments present (Fig. 2, a).

2. Stigmas perfect, reaching the mouth of the corolla; anthers present, but abortive, reaching two thirds the way to the mouth of the corolla (Fig. 2, b).

3. Stigmas perfect, reaching half way to the mouth of the corolla; anthers abortive or absent, not reaching the stigmas.

4. Stigmas imperfect, anthers perfect; both reaching the mouth of the corolla.

5. Stigmas imperfect, anthers perfect; both reaching two thirds of the way from the base to the mouth of the corolla.

6. Stigmas imperfect, reaching slightly beyond the mouth of the corolla; anthers perfect, reaching to the mouth (Fig. 2, c).

The relative proportions of the different forms seem to vary with the locality. The majority of specimens I have studied belonged either in the first or fourth category. The arbutus at