Boy Scouts Handbook / The First Edition, 1911

by Boy Scouts of America

Slab containing fossil shells

Conglomerate or pudding-stone

In many regions the beds of sedimentary rocks, which must have been nearly horizontal when formed, are now found sloping at various angles or standing on edge, the result of slow deforming of these beds at an earlier time. As some beds are more easily worn away than others, the hills and valleys in such regions owe their form and position largely to the different extent to which the harder and softer beds have been worn down by weather and by streams. The irregular line of many coasts is likewise due to the different hardness of the rocks along the shore.

It is by the study of the rocks and of the remains of life found in them, by observing the way in which the surface of the earth is being changed and examining the results of those changes and by concluding that similar results were produced in former times in the same way, that geologists are able to read much of the past history of the earth, uncounted years before there were men upon it.

Plants, Ferns, and Grasses
By Dr. L. C. Corbett, Horticulturist, United States Bureau of Plant Industry

The appearance of the blossoms and fruits of the fields and forests in any locality note the advent and progress of the seasons more accurately than does the calendar. Plants and seeds which have lain asleep during the winter are awakened not by the birth of a month, but by the return of heat and moisture in proper proportions. This may be early one year and late another, but, no matter what the calendar says, the plants respond to the call and give evidence of spring, summer, or autumn as the case may be. The surface of the earth is not flat. We have valleys and we have mountains; we have torrid and we have temperate zones. The plant life of the world has been adjusted to these varied conditions, and as a result we have plants with certain characteristics growing in the tropics at sea-level, but a very different class of plants with {118} different habits and characteristics inhabiting the elevated regions of this same zone. It must be remembered that even under the tropics some of the highest mountains carry a perpetual snow-cap. There is therefore all possible gradations of climate from sea-level to the top of such mountains, even at the equator, and plant life is as a result as varied as is climate. Each zone, whether determined by latitude or by altitude, possesses a distinctive flora.

But altitude and latitude are not the only factors which have been instrumental in determining the plants found in any particular locality. This old earth of ours has not always been as we see her to-day. The nature we know and observe is quite different from that which existed in earlier ages of the earth's history. The plants, the trees, and the flowers that existed upon the earth during the age when our coal was being deposited were very different from those we now have. There has been a change, but, strange as it may seem, there are in some places upon the earth to-day some of the same species of plants which were abundant during the coal-forming periods. These are among the oldest representatives of the plant world now extant. Then we are told that there was a period when the north temperate zone was covered with a great ice field which crowded down as far as southern Pennsylvania and central Ohio. This naturally brought about a profound change in the location and character of the plants of this region. There are in the Black Hills of Dakota species of plants which have no relatives anywhere in the prairie region, and no means is known by which these representatives of a Rocky Mountain family could find their way into the Black Hills, save that, previous to the ice age, this species was generally scattered over the territory, and that, during the ice age, the species was perpetuated in the hills, but was killed out between there and the Rocky Mountains where it is found in abundance. These are some of the natural reasons for the existence of varied plants in different localities. They are sufficient to explain the reason for the existence of local floras.

But nature has provided untold ways for the perpetuation as well as the dispersal of plants for the purpose of, so far as possible, enabling the plants of the world to take possession of all parts of the earth's surface. If this adjustment were complete, the plants would be practically alike all over the surface of the earth, but we have already explained why this cannot be and why we have a different flora in each zone, whether it be marked by lines of latitude or height of {120} the mountains. Plants are perpetuated by seeds, by bulbs, and by woody parts. Some seeds are highly perishable and must be sown as soon as ripe; others remain years without losing their power to produce plants. Some grow as soon as they come in contact with the soil; others must fall, be buried and frozen before they will germinate. Some plants are perpetuated by bulbs, tubers, or roots in which a supply of food material is stored away to carry the plant over a period when its above-ground parts cannot thrive owing to frost or drought. Upon the return of favorable conditions, these resting parts throw out shoots and again make the round of growth, usually producing both seeds and underground parts for the preservation of the species. There are both wild and cultivated plants in nearly all sections which illustrate these methods of preservation. Besides plants which have bulbs, tubers, or perennial roots, we have the large, woody plants which live many years and so perpetuate themselves, not only as individuals the same as plants with perennial roots; but they, too, as a rule, produce seed for the multiplication of their kind.