Littell's Living Age/Volume 140/Issue 1804/Miscellany

A Nettle-Sting. — Most persons have made an unpleasant acquaintance with one form of plant-hair through being stung by a nettle, but comparatively few have paid any attention to the exact nature of the offending organ, much less considered its relation to similar structures on other plants. The stinging hairs of the nettle belong to the class of "glandular hairs," and they consist of the glandular, or secreting part, at the base, and of the conical tube arising from it, and most often ending in a very sharp point. A simple plant-hair is an outgrowth from the epidermis, or plant-skin; but those with glands at their base may, as Sachs explains, be partly formed by cells of this epidermis, and by a layer of the vegetable tissue below them. A gland may consist of one or more cells. In the nettle there are several. The function of a gland is to separate some peculiar substance, such as oil, resin, camphor, etc.; or a poison, as in the nettle and other stinging plants. Many plants that have scent glands (sweet herbs, scented geraniums, etc.) easily yield a portion of their contents to slight pressure; the nettle as readily parts with its poison, which the sharp hairs insert into the skin of the person inadvertently touching it. If a vigorous leaf is examined under the microscope, or with a hand-lens of about an inch focus, each tubular hair will be seen wholly or partially filled with a colorless fluid. If while under examination one of these hairs is pressed with a needle, the fluid will be seen to move. If a glove is put on the left hand, a nettle-leaf twisted round the fore-finger with its upper side outermost, and held up to the light, the stinging hairs may be readily examined with a small magnifying glass in the right hand; and if any one of them is touched writh the nail of the middle finger a movement of the fluid contents will be noticed. A few hairs may be picked out of the leaf with a needle, taking also a little of the leaf tissue, avoiding injury to any part of the structure. The hairs may then be placed on a glass slide, covered with thin glass, and put under a microscope with an inch power. If the covering glass is pressed with a needle while the objects are under view, the fluid will be seen to run out, often without visible injury to the hair. One writer says that the well-known plan of grasping the nettle to escape its sting succeeds because the hairs are broken off below their sharp points, and cannot pierce the skin; but a great many trials show that the hairs are very often by no means so brittle as this notion supposes. Science for All.

The Norman Castles. — The castles built in the era immediately following the Conquest were very numerous, and, considered in connection with the enormous number of religious foundations, which date from the eleventh and twelfth centuries, the building activity of that age was, perhaps, unexampled. In their construction, everything was sacrificed to military necessities, without the slightest concession to any rival consideration. Not a stone was laid except in the strictest conformity with the conditions of the problem, and every inch of the structure, from basement to battlement, was the expression and result of a single purpose. The very profiles of the copings were devised to deflect or check the flight of the arrow, and indeed every part of the work bears testimony to the over-ruling sway of an iron age. The rough fancy of the Norman breaks out here and there in the ornament he loved so well, and with which the ecclesiastical buildings of the age abound, but never to the prejudice or even to the apparent weakening of the main purpose of the building. Cushioned capital, and zig-zag billet and chevron are found, but only in the crypt, or on some inner gateway, or for the adornment of the little oratory — seldom absent — nestling in the thickness of the mighty walls. Yet, in spite of the absence of deliberate artistic aim, the art instinct of their builders is everywhere felt. By fortuitous combinations of line and mass, the picturesque grandeur of the early castles is not exceeded by any of the works of man, nor is there probably any class of building the world over which has afforded the artist such universal aid and delight. To the novelist and the poet they are a never-failing source of inspiration. Need I mention Scott? The sight of a castle stirs his heart like the sound of a trumpet. Magazine of Art.