The agencies which serve to spread plants about over the earth's surface are very varied and interesting. Nature has provided seeds with many appendages which assist in their dispersal. Some seeds have wings, and some parachutes to take advantage of the wind. Some seeds are provided with hooks and stickers by which they become attached to the fur of animals and are in this way enabled to steal a free ride. Other seeds are provided with edible coverings which attract birds, but the seeds themselves are hard and not digestible; the fruit is eaten and the seeds rejected and so plants are scattered. Besides these methods of perpetuation and dispersal, some plants are perpetuated as well as dispersed by vegetative reproduction, i. e., by cuttings as in the case of willows; by runners as in the case of the strawberry; and by stolons as with the black raspberry. (For further information on this point see Bailey's "Lessons with Plants.")
Some plant characteristics, however, of greatest interest to the scout may be enumerated. Plants not only mark zones, but they indicate soils with certain characteristics, and the crop wise say that the soil on which chestnut abounds is suitable for buckwheat or peaches. Plants also indicate the influence of local conditions such as lakes, ponds, or even variations in contour. A knowledge of the local flora of a region will at once tell one whether he is upon a northern or a southern hillside by the plants of the area. The creek bottom will {121} abound with species not to be found on the hillsides, but species common to both plain and mountain will mark the progress of the season up the slope.
In the north temperate zone the moss if any will be found growing upon the north side of the tree trunk. Each hundred feet of elevation in a given latitude makes from one to two days difference in time of blooming of plants. The character of the vegetation of a region is an index to its climate. Certain plants are adapted to frigid regions, others to temperate, and still others to tropical areas. Some plants are adapted to humid sections, while others are admirably adjusted to desert conditions. A knowledge of these differences in plants will be of the greatest value to the scout, and if this is supplemented by information about the value and uses of the various plant products many hardships can be avoided. Many plants produce valuable juices, gums, and resins, while others yield us valuable timber for building and cabinet uses.
While it is impossible to even suggest the great variety of plants found within the confines of the United States, the following books on botany will be found helpful in each of the different sections for which they are designed.
Bibliography
For the botany of the Northeastern United States use:
"New Manual of Botany," 7th ed. Asa Gray.
"Illustrated Flora of the United States and Canada." N. L. Britton and Hon. Addison Brown.
For the botany of the Southern United States use:
"Flora of the Southern United States." A. W. Chapman.