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vation. Theophrastus and Pliny both made some ecological observations which were destined to play an important part in investigations of the future.

WHAT THESE MEN OBSERVED

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Let us frankly recognize the service these men rendered to increase our knowledge of plants. The plant pathology of these earlier writers was primitive of course and the plant pathologist of to-day would hardly class this early work under that term. This knowledge of the ancients was buried for centuries, in which little attention was given to botany or related subjects, but we may feel sure that during the "Dark Ages man was intensely interested in the economic phases of botany although we have little written evidence of such interest. Botanists of long ago paid some attention to medical botany. We need only recall that such treatises as Gerard's "Herbal" and later the painstaking work of Hayne, "Die Arzneigewäshse," Rafinesque, "Medical Flora," and many others of the old writers up to the modern work of Millspaugh, "American Medical Plants," Kraemer, " Pharmacognosy," and Luerssen, Handbuch der Systematischen Botanik," have kept us up with the times.

We know that the Crusaders brought from Asia and eastern Europe medicinal plants, cereals and fruits that made possible the highest type of civilization, for improved plants accompanied a revival of learning. We may be sure that during this epoch the economic phases of plants were studied because of the importance of increasing the food supply. The knowledge gleaned was passed on to the next generation to be of some use to man, and followed by the work of others who for the most part were observers, and our science, it must be said, began in observation. Men like Robert Morison, a close student of Cesalpino, Kasper Bauhin and others, added a little to the knowledge of previous botanists. John Ray and Francis Willoughby became interested in another phase of economic botany; they conducted experiments on the motion of sap in trees. Ray was generous to his prede

cessors like Grew, Jung and Malpighi. The old myth that wheat will degenerate in chess probably started with Ray, because he published a statement that Triticum could be changed into Lolium. Malpighi, the father of microscopical anatomy, gave a fair account of the structure of plants, including the ducts and the Malpighian cell. Economic plants always received special attention.

The English philosopher, Robert Hook, gave a fair account of cork, which he had studied with his improved compound microscope. He investigated the nature of food of plants.

Grew, in his "Anatomy of Plants," outlines in a masterly way the architecture of plants, interwoven however with the philosophical and theological prejudices of the time.

Bachman, who was a botanist, physiologist, pharmacologist and chemist, appreciated morphology and taxonomy. He introduced binomial nomenclature, and the reason given by him was that a prescription could be written easier. Think of it, that we as botanists are indebted to medicine for the naming of plants. Bachman refused to recognize cultivated varieties as species. Tournefort had only to go a step to recognize genera which he did in a splendid way. The last link in the chain of the botanists who were influenced by the older school was Linnæus, who borrowed from his predecessors like Cesalpino, Jung, Bachman and others, but always with fulsome praise of the work of his contemporaries and prede

cessors.

Sachs says:

We are astonished to see the long known thoughts of these writers (Bauhin, Cesalpino, Jung), which in their own place look important and incomplete, fashioned by Linnæus into a living whole; thus he is at once and in the best sense receptive and productive.

Linnæus thought it important to know all species of plants. His "Philosophica Botanica" was a splendid text-book of botany. There was nothing else like it for more than a generation, at least there was nothing that equalled it in clearness and completeness. He

was not an experimenter and cared little for it. In Germany, under his influence taxonomy degenerated into mere plant collections, collectors calling themselves taxonomists.

POST-LINNÆAN BOTANY

A new era opened with such men as Jussieu, Gaertner, DeCandolle, Robert Brown, Adanson, Endlicher who knew how to observe and interpret the things they saw. Experimental work with plants became more important; botanists began to ask the why about plants; and so E. Mariette, one of the first experimental physicists, studied the salts of plants and the active forces of attraction and nutrition.

Martin Lister directed attention to the movement of water in plants. Christian Wolff, too, experimented on the nutrition of plants. Stephen Hales in his "Statistical Essays" sought to trace back the phenomena of vegetation to mechanico-physical laws, as then understood, and studied the water taken in by plants and its exit by the leaves and the formation of solid substances.

The discovery of oxygen by Priestley was important in plant physiology, but he missed the important discovery that light is a vital factor in making plant food. This was left to Jean Ingenhousz, whose experiments showed that purifying of air goes on in light only. This led him to study the food of plants and the improvement of soils. He discovered that plants use CO. and under the influence of light make plant food. Jean Senebier was the first to give a clear statement of the process of photosynthesis. We are indebted to the chemist, DeSaussure, for his discoveries, which laid the foundation in an experimental way of the process of food-making in plants. It is a long way from the researches of these pioneers to the work of Boussingault's quantitative methods of studying the food requirements of plants, especially with reference to nitrogen, and the work of Sprengel on ash constituents and Liebig's work, "Chemistry in its Relation to Agriculture and Physiology." These greatly helped to advance plant physiology, as did also the work of Lawes and Gilbert on the mineral constituents of plants and later the

pot culture method of Knop, Sachs, and the work of Lachmann, who in 1858, spoke of the "Vibrionenartige" organisms found in leguminous nodules. Later the work of Schloesing and Muntz, Warrington, Beijerinck, Winogradsky, Hellriegel and Wilfarth and many others made secure for ever a better agricultural practise. Added to the knowledge of the importance of the legume bacteria the important discoveries of Wollny and Berthelot show that bacteria in the soil are the makers of plant food.

Plant physiological work in Europe made rapid strides through the labors of Detmer, Pfeffer, Sachs, Jost, Palladin, Haberlandt and many others. The question of photosynthesis long remained obscure because of insufficient chemical study of the plant pigments. The environmental factors were partially determined by F. B. Blackman and then Willstatter and his coworkers determined the chemistry of chlorophyll, which enabled plant physiologists to better understand the problems of carbon assimilation. Jorgensen and Walter Stiles in their résumé say:

No prophetic vision is needed to foretell development in plant physiology as great as those which were produced by physics and chemistry in engineering and other technical sciences.

It is refreshing to observe that a soil physicist like Edward Russell in his paper "Soil Conditions and Plant Growth," should put stress on plant physiological problems as fundamental to a study of soils and plant nutrition.

Jung did not entertain any definite idea of the sexuality of plants nor did Grew have a clear conception. Rudolph Camerarius, however, settled the problem by making experiments with maize and mulberry, two economic plants.

We can only marvel at the economic trend of the work of Leewenhoek in the study of linen, who made the discovery of minute organisms, and thus repudiated the theory of abiogenesis. People became curious to study the hitherto unseen world. The use of the microscope in the hands of the curious was

not for scientific or practical purposes, but gave source to wild speculations in disease and the origin of life. However, its useful day came many years later, when its discoveries were made use of in many practical problems, connected with disease of plants and animals and the physiological problems in connection with crop production.

PLANT PATHOLOGY

Meyer, an extraordinary man who died at the age of thirty-six, published a work on phytopathology, a paper on corn smut and one on actinomyces. He was a physiologist and looked at the problem of disease from the standpoint of physiology, really the only way the subject should be treated. Camerarius seems to have antedated the work of Meyer by over one hundred years in the publication of his paper "De Ustilagine Frumenti." Julius Kuehn was primarily an agriculturist and as director of the Agricultural Institute at Halle started a series of experiments on plants that have become classic. While thus engaged in the work he became interested in a study of the diseases of plants. To him we owe the first comprehensive treatise on plant pathology. He had breadth of vision to study and interpret what he saw with the microscope and thus there came into being "Die Krankheiten der Kulturgewächse," which stands as a monument to his labors. It is the only botanical paper by him listed by Pritzel in his Thesaurus. M. J. Berkley's work, "Introduction to Cryptogamic Botany," gave to Englishspeaking people the first real treatise on plant diseases, which laid a sure foundation for a study of plants, along economic lines.

All of the work on plant diseases and the anatomy of plants was better established later through the classic work of DeBary.

De

Bary, of course, did not have, except in some cases, the practical problems in mind, though the science of botany and plant pathology in particular have been greatly benefited through his profound researches in connection with the development of life history of fungi. DeBary brought to the science of mycology a

a

breadth of knowledge along many lines of botany and one marvels at the enormous amount of research work he did. Nor should we omit to mention the great work of Tulasne (who had the merit of first breaking the ground in a study of rust, smuts and ergot), on the discovery of the germination of the spores of rusts, smuts and the sexual organs of Peronospora. While these researches did much for mycology, indirectly they have been of great practical importance to pathology. Robert Hartig, perhaps the foremost student in the world during his lifetime of the diseases of forest trees and the decomposition of wood, exerted a great influence on the practise of forestry, followed later by the splendid work of Marshall Ward, a student of Hartig. We may mention in this connection the work of Fischer de Waldheim, Wolff, Sorauer, Appel, Millardet, Prillieux, Jones, Halsted, Arthur, Bolley, Atkinson, Stewart, Whetzel, Freeman, Clinton, Thaxter, Duggar, Stakman, Cook, Stevens and Melhus. These as well as host of others, added to this economic phase of botany, making secure the science of plant pathology. I need only add here that the stimulus given by these men to this economic phase of botany has been communicated to all parts of the world; and SO we may mention especially the pioneer work by Dr. Farlow on Gymnosporangium, grape vine mildew, onion smut, Dr. Burrill on apple blight and sorghum blight, the epochmaking researches along the line of bacterial diseases of plants by Dr. Erwin F. Smith. Surely America may well be proud of its achievements. The present age has hundreds of new problems in plant pathology. The superficial only was touched on by the early workers. We may mention especially the root disease of cereals and other crops. The plant pathological studies on these parasites has changed our methods of agriculture completely. We need more careful and profound work on many of the problems worked upon by the pioneers. The pioneers who blazed the way may be excused for errors, but the modern investigator should not be. He has the

equipment and money and should do good work.

POLLINATION OF FLOWERS

Another phase of the subject of economic botany is that of pollination. Progress was slow. Geoffroy, who as early as 1711 made some observations on the nature of the style, is said to have conducted some experiments with maize; however that may be he did make use of the work of Camerarius. Geoffroy concluded from various sources that fertilization was a kind of fermentation, but he was inclined to accept a second view of Morland that the pollen grains contain the embryo which find their way to the seed. We may also recall the work of John Logan, at one time governor of the colony of Pennsylvania, who conducted experiments on the fertilization of maize, in which he noted that cobs covered with muslin did not produce seed, but seed was formed on cobs where pollen came in contact with the stigmas. Logan suggested that the wind carried the pollen. Gleditsch in a study of one of the palms (Chamarops humulis) strewed loose dried pollen on the stigmas of a female plant which produced seed which later was planted and germinated; a simple experiment but a convincing one to the botanists of the time, who had never seen pollination demonstrated before. Philip Miller in 1751 calls attention for the first time to the importance of insects in the pollination of tulips. The first scientific experiments on hybrids were made by Koelreuter, who discovered the use of nectar and the importance of insects in the pollination of flowers. Koelreuter clearly set forth the facts that the mingling of two substances produced a seed. These general statements as set forth by him still hold true. He was a skillful experimenter in the hybridizing of plants. The work of Sprengel on the pollination of flowers is well known to the older botanists. His sharp discriminating observations on the relation of insects to flowers were little understood at the time. The full import of these problems were recognized by Charles Darwin, who in his masterly way showed the application of this

in practical problems. Earlier Sir Andrew Knight had demonstrated "that no plant fertilizes itself through an unlimited number of generations." Dr. Gray put this in a much more terse way. A score of investigators like Hermann Mueller, Fritz Mueller, Delpino, Ludwig Axell, Hilderbrandt and in our country men like Gray, Trelease, Riley, Foerste, Beal and Robertson demonstrated the use of insects in pollination and the application of this fact to important agricultural crops. These fundamental facts are fully recognized to-day in the growing of apples, alfalfa, sweet clover, melons, squash and cucumbers. The orchardist recognizes the importance of bees in connection with the growing of apples, pears and plums. The farmer recognizes the importance of bees in the alfalfa and sweet clover fields, just as Charles Darwin recognizes that the bumble bee is important in the red clover pollination. In this connection, as an economic problem, I may call attention to the honey flow in flowers. It is true beekeeping is only one of our minor agricultural problems dependent entirely on the relative abundance of honey plants in a given region. There are a great many interesting physiological problems in connection with nectar secretion, as Kenoyer has shown. One wonders why alsike clover scarcely yields any nectar for bees in Iowa and yet in some regions of the country it is one of the best of nectar plants. There is seldom any nectar in buckwheat flowers after 10:00 A.M. in Iowa, and yet in sections of the United States the period of nectar flow is much longer. Is soil alone a factor or is moisture an important factor, or are the two factors combined? We have enormous expanses of waste land along our highways in the United States, why not combine the esthetic with the economic if we can find plants that are suited for such places that will yield good returns for the beekeeper.

PLANT BREEDING

I heard a practical fruit grower in Iowa say the other day when a new chance seedling apple was shown me that nearly all of the new good things in the fruit line are chances; that

is to say the new productions by Burbank, Hansen, Patten, Beach, Hedrick, Webber and many other plant breeders are not equal to those found in nature. I need only recall the many fine things the modern plant breeder has produced. Of course, new types will always appear, as they have in the past. The work accomplished, it seems to me, will justify larger expenditure of money.

In the matter of fundamental study of these problems practical agriculture, horticulture and floriculture are indebted to the classic fundamental work of Hoffmeister and Strasburger. This work led up to and explains the physical basis of Mendelism discovered by Gregor Mendel, a work that is most important in the breeding of new types. We have had a host of botanical investigators who have enhanced our knowledge of plant breeding, linking it with practical work like Nilsson, Johannsen, Bateson, Correns, Shull, White, Webber and Emerson. Agriculture and horticulture are indebted to the epochmaking work of DeVries on mutation. His work has set a score of botanists to work on the pedigree culture work. I may mention Nilsson, Johannsen and Gates especially. Possibly the outstanding problem of the pomologist in states like Iowa and Minnesota is that of hardiness. In breeding experiments at the present time it is necessary to set the trees out and test them for a term of years, to see whether or not this climate is too severe. Bakke in some recent experiments has found that by ascertaining the depression of the freezing and the moisture content at a time when all the tissues are in an active state of growth, it is possible to obtain an idea of the comparative hardiness of different apple trees. These tests have been made upon trees in the nursery as well as upon trees in an orchard, 10 years old, with practically the same results.

SEED STUDIES

After a consideration of pollination the matter of seed is of importance. The first great work published is that of Gartner, "De fructibus Seminibus plantarum." Gartner was free from the bias of those who preceded him.

We have a truly modern work by one whom we may regard as a modern man of science. He made a comparative study, correctly determined the relation of the endosperm to the cotyledon and named the embryo. We have had a long line of investigators on the subject of seeds.

The practical application found expression in the work of Nobbe, Harz and others. We may recall the work of Nobbe in the testing of seeds at the small experiment station at Tharand, which was the beginning of the experiment stations such as we know them today. Nobbe did not merely do the mechanical part in connection with the testing of seed, but inquired into real scientific problems in connection with specific gravity, and the vitality of seeds under different conditions of storing. The germination of many seeds is of special concern to the agriculturist, because it is important to know under what conditions a seed will germinate best to bring the largest returns. It is a matter also of some concern for the farmer to know whether weeds' seeds have a varying period of vitality when buried in the soil, whether for instance the seeds of Hibiscus Trionum and Abutilon Theophrasti will come up in his fields after a quarter or half a century when he practises rotation of crops. The vitality and structure of seeds has of course received much attention. I need only recall the classic work of DeCandolle who more than a century ago studied the prolonged vitality of seeds. The data secured by DeCandolle is frequently quoted in text-books of plant physiology. Also much later work of Becquerel, Beal, Ewart and Hanlein on delayed germination, as well as the work of Crocker and his students like Shull, on the delayed germination of seeds, like wild oats and other seeds of economic importance. To Crocker we are indebted for an explanation of the delayed germination of such seeds as the cocklebur. Knowing that there is a delay in some seed the farmer is better able to follow a rational practise in the treatment of seeds. I am sure that most of you are familiar with the work of Schleiden and Vogel, Chalon, Malpighi,

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