Page:Popular Science Monthly Volume 6.djvu/134

This page has been validated.
124
THE POPULAR SCIENCE MONTHLY.

amine the under surface with the microscope after the separation of the cuticle, the peculiar and characteristic space between the two cells of the stomata is readily perceived. The long unicellular hairs of the tea-leaf are also peculiar. The employment of caustic potash is desirable in observing these characters.

"In the sloe-leaf the serratures are direct incisions, numerous, often irregular, and extending down to the base. There are no spines. The hairs are shorter and coarser than those of the tea-leaf, and are marked in a peculiar manner. The elder-leaf is more pointed than that of the tea-plant, and the lobes are unequal at the base. The serratures are direct incisions. The midriff has hairs on it, and on the leaf itself there are several kinds of hairs, notably a short, spinous, striated hair, which occurs on the upper surface. The serratures of the willowleaf much resemble those of tea, but the cell-walls of both the upper and under epidermis differ from those of the tea leaf in not being sinuous, and there are long, coarse, striated hairs. When perfect, the elongated form of the willow-leaf sufficiently distinguishes it from tea, and the venation is also entirely different. The chief foreign leaves added by the Chinese are those of Chloranthus inconspicuus and of Camellia sasanqua, the latter of which presents a close resemblance to the tea plant."

 

Usefulness of the Robin.—Pitying the ignorance of farmers, and country-people generally, touching the habits and usefulness of the robin, and pitying equally the poor bird itself for the abuse which this ignorance brings upon it, Caroline Bryce, in the April Naturalist, has rendered a service to both by pointing out in a very interesting way the value of the bird to the country, and the mistake that is made in attempting to drive it from our fields and groves. "The robin has two broods in a season, each brood varying in number from two to five. The young are fed exclusively on insects, and their rapid growth and consequent voracity, only equaled by the larvae stage of insect-life, makes an abundant supply of insect-food an indispensable requirement. The food of the mother-bird is also chiefly insects, and this double demand makes the robin a valuable assistant to the farmer and horticulturist in keeping under insect pests. Regarding its supposed habit of cherry-eating, the author is of opinion that it is attracted chiefly by the color of the fruit, and not by any special liking for it as food; that it picks the cherries for the same reason that it picks to pieces a red flower. Instead of being an enemy to the cherry-crop, it is in reality a most important aid in securing an abundant supply of healthy fruit. If I should venture to say that not a cherry would grow, fit to be eaten, were it net for the birds, the bare idea would be hooted as preposterous, yet such, nevertheless, is my belief. Were it possible to remove all the birds out of the way, for one season at least, what a decided difference would our future orchards present! Where now are thrifty growths, beautiful leafage, and large crops of fair fruit, would be seen stinted, moss-grown limbs, with sparse or meagre foliage, crops of dwarfed specimens, that have finished their growing, in a knotty, wormy, inferior state. The majority of all the large families of insects are bred in the earth, and go through various forms in different stages of existence, and are devoured by birds of every description, chief among which stands our friend the robin."

 

How Leaves are blanched by Bright Sunlight.—The leaves of certain plants grow pale in the full glare of the sun, and it becomes a question whether this change is due to a diminution of the amount of chlorophyll. Mr. H. C. Sorby has repeatedly analyzed the leaves of such plants, but the result showed that sunlight or shade makes no difference in the quantity of the chlorophyll. He therefore came to the conclusion that the change in color is due to some mechanical alteration in the structure of the leaves. This conclusion is confirmed by the independent researches of a French observer, Prillieux. According to the latter, exposure to bright light causes both granular and amorphous chlorophyll to collect together at the sides of the cells, instead of being more evenly distributed. The result is, that a much larger relative quantity of white light is reflected, and the leaves appear of a paler and whiter green.