posites it is the calyx; in the bulrush the perianth; in Epilobium the crown of the seed; in the cotton-grass it is supposed to represent the perianth; while in some, as, for instance, in the cotton-plant, the whole outer surface of the seed is clothed with long hairs. Sometimes, on the contrary, the hairs are very much reduced in number, as, for instance, in some species of Æschynanthus, where there are only three, one on one side and two on the other. In this case, moreover, the hairs are very flexible, and wrap round the wool of any animal with which they may come in contact, so that they form a double means of dispersion.
In other cases seeds are wafted by water. Of this the cocoanut is one of the most striking examples. The seeds retain their vitality for a considerable time, and the loose texture of the husk protects them and makes them float. Every one knows that the cocoanut is one of the first plants to make its appearance on coral islands, and it is, I believe, the only palm which is common to both hemispheres.
The seeds of the common duckweeds (Lemna) sink to the bottom of the water in autumn, and remain there throughout the winter; but in the spring they rise up to the surface again, and begin to grow.—Fortnightly Review.
[To be continued.]
|SUNSTROKE AND SOME OF ITS SEQUELS.|
UNDER the designations of sunstroke, coup-de-soleil, heat-apoplexy, heat-asphyxia, thermic fever, ardent fever, insolation, and others, are included certain pathological states which, though differing from each other materially, are not unfrequently confounded.
1. There is simple syncope from exhaustion caused by heat.
2. A condition analogous to shock, due to the action of the direct rays of a powerful sun on the brain and cord; the nerve-centers, especially the respiratory, are affected; respiration and circulation rapidly fail, and death may result; recovery is frequent, though not always perfect.
3. Overheating of the whole body, blood, and nerve-centers, either from direct exposure to the sun's rays, or, more frequently, to a high temperature out of them; causing vaso-motor paralysis and intense pyrexia (fever); respiration and circulation fail, and asphyxia follows. Recovery frequently occurs, but is often incomplete, owing to structural changes in the centers, giving origin to a variety of symptoms indicative of lesions of a grave character.
The cases of simple exhaustion and syncope may occur during