Popular Science Monthly/Volume 47/July 1895/Herbaria in Relation to Botany
|HERBARIA IN THEIR RELATION TO BOTANY.|
THE offer of Captain Donnell Smith to Johns Hopkins University of his valuable herbarium and library gives us an excellent opportunity to consider what such herbaria are, how they are brought together, and what is their purpose. We intend, furthermore, to show what they accomplish in botany and what botany does besides.
The importance of Captain Smith's gift will then be evident, and the value of a well-equipped botanical department to the Johns Hopkins and to the community at large will also be clear. The references to flowers and trees in ancient poems show that the beauty of vegetable Nature was fully appreciated at an early period, and agriculture requires the rudiments of a scientific knowledge of plants; but the first systematic attempts to study botany scientifically owe their origin to the desire to know more of plants in their relation to medicine. There are few plants which have not at some time been supposed to have great medicinal value, as the number of those designated officinalis clearly indicates.
The first systematic study of plants in their relation to medicine was in the Athenian Republic, and Theophrastus, Dioscorides, Pliny, and Galen are especially known for their writings on this subject. During the middle ages the science of the Greeks was forgotten, and interest in their investigations was not revived till the sixteenth century. By this time the old Greek texts had become greatly obscured by imperfect translations, and it required much patience and care to recognize plants from their descriptions. The botanists of the sixteenth century, like Bock, Fuchs, and Mattioli, working in Germany, found another difficulty in the circumstance that plants of their country differed widely from those in Greece. This, together with the imperfect state of the old descriptions, gave rise to frequent mistakes in identification. Some other authors, however, would notice the error, and disputes often arose, which sometimes became violent. The great value of this work to us is that it showed the necessity for more exact descriptions of plants, and this, combined with the occasional finding of new plants of a supposed or real value to medicine, gave rise to those large parchment-bound, queer-looking old volumes on botany which, besides the descriptions, often contained very beautiful pictures of the plants. These were then called herbaria, a significance being given to the word which it has now lost. It soon became painfully evident that very good and conscientious descriptions, even when accompanied by accurate plates, were yet not adequate to express all those delicate details which the living plant showed. So some of the authors found a way to keep the plants they had described, at first for their own reference, and for this purpose dried them carefully, glued them on sheets of paper, and put the name on this paper. Preserved in this way and arranged alphabetically for easy reference, these specimens formed a supplementary confirmation of their descriptions which was readily accessible. This was what we now call a herbarium—in other words, a collection of well-preserved, carefully named dry plants. If the description of an author who had a collection of this sort was called in question, it was an easy thing for him to send his original plant to some third botanist, who could decide whether he was right. Afterward it was recognized by those who described new plants that it would be of great importance to them if they could have the originals of the descriptions of their fellow-botanists. So a system of interchange of originals arose, which is now carried on between botanists all over the world. A trained and competent botanist who finds an opportunity to study the flora of regions which are little known may by this means become possessed of all the most instructive and remarkable plants that are known to science.
So a modern botanist no longer collects, as was formerly done, only one or two samples of every plant, but one or two hundred—of rare species often two thousand—because every specimen he has will enable him to obtain some new one in exchange.
The difficulties of collecting in the present time may be estimated from this. To collect four thousand plants in a tropical climate means not only to find, dry, and name these under the most unfavorable conditions, but to prepare perhaps forty thousand, all the duplicate specimens being used in exchange.
For a long while plants were named by any word which took the fancy of its author, and were arranged in the alphabetical order of the names. Soon, however, it was found that a better disposition was desirable, as nobody could look over such extensive alphabetically arranged collections, and students began to assort the plants in such a way that those which had certain characteristics in common were grouped in classes. So, for example, all kinds of grasses, all kinds of trees, all kinds of shrubs were put together, etc. Such a beginning of classification and unconscious recognition of relationship was begun by Lobelius and Bauhin, extended by Cæsalpin, and completed by Linnæus. Linnæus, besides, saw the necessity of bringing together all the descriptions of plants already existing, and of wording them in such a way that, without losing anything essential in the description, they should occupy the smallest possible space. Such a condensed description is now known as a diagnosis.
When he had accumulated a considerable number of diagnoses he saw that it was difficult to find one's way through them, and he set about arranging them after some of the most striking characteristics which did not necessarily indicate relationship, but were simply as a means of classification and recognition. He took for this first the number of stamens, bringing all plants with one stamen in the flower together, all with two, three, four, five, ten, etc., into their several classes, in this way creating the groups of the Monandra, Decandra, Polyandra, etc.
Having done this, he recognized that a subdivision of these groups was desirable; that many plants with the same number of stamens yet differed considerably among one another; and these smaller groups he called genus, plural genera. Such a genus now, for example, is the buttercup, which he called Ranunculus. He saw that further subdivision could take place, and that there were a great many plants which, though evidently all buttercups, yet differed sufficiently to be distinct. So he resolved to give every plant two names, the first one being the genus name, here Ranunculus, the second one expressing some property of that particular kind of Ranunculus, and thus indicating the species. Thus he found, for example, that one buttercup had an acrid taste, and he called it the acrid buttercup—in Latin, Ranuncidus acris; that another one always grew on marshy places; he called it the marsh buttercup—in Latin, Ranunculus palustris, etc.
Latin names were used simply as a matter of convenience, as it was much easier to know one Latin name than a dozen names in a dozen different languages for the same plant. Linnæus's system was consequently one of mere convenience and thoroughly artificial.
It had, however, already been recognized that certain plants belong naturally together, as grasses, for example, while Linnæus's system often placed two grasses very far apart. This conception of relationship, however, could not be expressed well before Darwin had shown that plants had not always been as they are now, but that the higher plants had gradually been developed from the lower ones. Then an entirely different system arose—a system which expressed the relation of plants in the way of a genealogical tree; this system is generally known under the name of the natural system. It is after this natural system, which expresses our conception of the blood relation between the different plants, that our present herbaria are arranged, 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.
- Read before the Scientific Association of the Johns Hopkins University, February 21, 1894.