Page:Popular Science Monthly Volume 47.djvu/375

Rh and it is their object to show us at all times not only the plants described, but also the family relation between these different plants.

In Linnæus's time a botanist was regarded as somebody who could name at sight any plant presented to him, and the best botanist was the one who was most proficient in this. We are justified, however, in requiring a few other things from a good botanist. The recognition of the family relations between different plants gave rise to the comparing of their different organs, to the study of their development, to inquiring what conditions had influenced an organ in such a way that it became modified, to the search for the equivalents of the organs of the higher plants among the lower ones; all of which constitute that branch of botany which now is known as morphology.

The recognition of yet finer details created our histology.

The closer acquaintance with plants induced scientific men to observe their habits, their distribution, and how they lived; and this is plant physiology in its widest sense.

For the study of the botanical system, morphology, and geography, a herbarium like that of Captain Smith is of the greatest advantage. For physiological purposes, quite other things—as exact instruments, hothouses to keep living plants, etc.—are necessary.

Physiology is that part of botany which has had most practical value. The fertilizing with artificial manures is entirely founded upon it, for it never could have become known if careful experiments in the laboratory had not shown what substances were necessary to each particular kind of plant. Consequently, all agricultural experiment stations are practically based on plant physiology.

This plant physiology, or the science of the normal life of the plant, gave rise to the study of the plant under abnormal—in other words, diseased—conditions, and so the science of plant pathology, on which our knowledge of the diseases of our crops and the way to prevent or cure them is based.

Last, and not least, the study of those very smallest plants, the bacteria, made an enormous change in our treatment of sick human beings; the study of the parasitic molds has done an important service to our fish industries; so the influence of modern scientific botany is felt in fields that seem to the casual observer to have no connection with vegetation, and the scope of this science is no longer confined to what for years was its only object—the naming of plants.