Posts by Tatiana

When settling itself to sleep, the Toucan packs itself up in a very systematic manner, supporting its huge beak by resting it on its back, and tucking it completely among the feathers, while it doubles its tail across its back just as if it moved on hinges. So completely is the large bill hidden among the feathers, that hardly a trace of it is visible in spite of its great size and bright color, so that the bird when sleeping looks like a great ball of loose feathers.

Silicon is always considered as a non-essential element, although it occurs in such large proportions in some plants as to indicate that it cannot be wholly useless. It accumulates in the stems of plants, chiefly in the cell-wall, and has sometimes been supposed to aid in giving stiffness to the stems. But large numbers of analyses have failed to show any direct correlation between the stiffness of straw of cereal plants and the percentage of silicon which they contain. Further, plants will grow to full maturity and with erect stems when no silicon is present in the mineral nutrients which are furnished to them. On the other hand, certain experiments appear to indicate that silicon can perform some of the functions of phosphorus, if soluble silicates are supplied to phosphorus-starved plants. But under normal conditions of plant nutrition, it seems to have no such function.

The stems of some plants, such as the Big Trees of California, for instance, are among the oldest and most permanent of living things. “General Sherman,” one of the biggest in that most famous grove, was nearly three thousand five hundred years old when Columbus discovered America; it has lived through all the great periods of modern history, and to-day it is over 270 feet high and 35 feet in diameter. No living thing is so large or has lived so long. In Australia are great forests of blue gum trees even taller than our Californian Big Trees, but not so old nor so thick.

It must be clear enough from the start that to call a leaf a factory for the making of food forces us to decide at once whether this is a mere way of speaking, or whether, incredible as it may seem, anything as thin as a leaf can really produce food. As we eat lettuce, and millions of cattle graze every day, leaves as food producers win handily on that score. But to understand how food is produced in such a tiny factory demands that we walk about in it for a bit, study the inside of it and especially its many small chambers within which is not only the machinery, but some of the finished product stored up for later use.

Unlike modern factories there are many entrances, from any one of which we can begin our tour of inspection. On the under side of nearly all leaves and on the upper side of some there are scores or even hundreds of small pores called stoma, so small that only with a microscope can they be seen. These entrances through the factory wall, are carefully guarded by a pair of watchmen whose business it is to see neither too much dry air gets in nor too much of the product of the factory gets out. They see to it, also, that waste products are thrown out at the proper time. These watchmen, or guard cells, as they are called, are constantly on the job, work almost automatically, but their chief function is connected with the proper ventilation of the place, and will be discussed later under “How Plants Breathe.”