CHAPTER VI PAGE
FAMILIES OF GYMNOSPERMS
77
Order Cycadofilicales, 79 . Order Bennettitales, 80. Order Cycadales, 81. Order Cordaitales, 82. Order Ginkgoales, 82. Order Coniferales, 83. Pinaceae, 84. Taxodiaceae, 86. Cupressaceae, 88. Order Gnetales, 89.
CHAPTER VII
FAMILIES OF DICOTYLEDONS
91
"^Magnoliaceae, 94. Berberidaceae, 97. Ranunculaceae, 99. v^ymphaeaceae, 102. ^Malvaceae, 104. Ulmaceae,
- Geraniaceae, 108. Linaceae, 109. ^utaceae, 111.
N^tuphorbiaceae, 113. Violaceae, 115. VKapaveraceae, 116. ^IJructferae, 117. Caryophyllaceae, 120. Chenopodiaceae,
Polygonaceae, 123. Salicaceae, 125. Ericaceae,
Gentianaceae, ^O.^'Oleaceae, 132. ^Asclepiada-
ceae, 133. ^Convolvulaceae, 135.*^olanaceae, 137. ^'feora-
ginaceae, 139.l^>crophulariaceae, 140. Orobanchaceae,
142.vtabiatae, 144. Rosaceae, 145. Pomaceae, 148.
Drupaceae, 149.^Leguminosae, 151. Saxifragaceae, 157.
Grossulariaceae, 158. Onagraceae, 159.^^Iucurbitaceae,
- Cactaceae, 163. Vitaceae, 165.V^Loranthaceae, 167.
Aceraceae, 168. VXnacardiaceae, 171. Juglandaceae, 171. Fagaceae, 175. Betulaceae, 179. Cornaceae, 182. ^Cm-
belliferae, 184. ^ubiaceae, 187. Caprifoliaceae, 188.
%/Compositae, 189.
CHAPTER VIII
FAMILIES OF MONOCOTYLEDONS
194
Alismaceae, 195.^Liliaceae, 196. Juncaceae, 199.UAra-* ceae, 200. -Palmaceae, 202. Cyperaceae, 202.iXJramineae, 205. Comparison of three families of grass-like plants, 211. Iridaceae, 211./Orchidaceae, 212.
CHAPTER IX
NOMENCLATURE
217
Relation of nomenclature to taxonomy, 217. Common names, 217. Botanical or scientific names, 219. Nonvalid names, 222. Citing authority for names, 226. Efforts
CONTENT*
xiii
PAGE
toward uniformity, 228. International botanical con-
gresses, 228. 'The type concept, 231. Digest of rules of
botanical nomenclature, 234. Effects of rules of nomen-
clature, 236.
CHAPTER X
PRINCIPLES OF TAXONOMY
237
Difficulties in classification, 237. Bases of taxonomy, 242. Plan of taxonomy, 249. Categories used in taxonomy, 249. The newer species concept, 253. Subspecific categories, 256. Contributions of other branches of botany to taxon- omy, 259. The experimental method in taxoYiomy, 262. Major and minor characters, 264. Clear-cut versus intergrading characters, 265. Homologs versus analogs, 267. Characters of Spermatophyta, 269. Morphological indicators of phylogeny, 276.
CHAPTER XI
SYSTEMS OF TAXONOMY
281
Pre-evolutionary systems of taxonomy, 281. Taxonomic development in southern Europe, 282. Taxonomic development in central Europe, 283. Evolutionary systems of taxonomy, 288. Comparison of the systems of Engler and Bessey, 296. Competition of systems, 300. Present status of angiosperm classification, 302.
CHAPTER XII
THE LITERATURE OF SYSTEMATIC BOTANY
305
Media for taxonomic publication, 305. The early classics, 306. Fundamental principles morphological, 307. Fundamental principles genetic, etc., 309. Rules of botanical nomenclature, 312. World floras and taxonomic systems, 314. Regional floras and manuals, 316. Taxonomic treatment of limited groups, 319. Cultivated and economic plants, 322. Non-technical floras, 324. Paleobotany, 326. Indexes, catalogues, etc., 327. Miscellaneous, 329.
Index
331
WHAT IS SYSTEMATIC BOTANY?
Systematic botany is the science of classifying and naming plants. Plant taxonomy lays emphasis on classification as an
expression of phylogenetic relationships, and nomenclature
provides each species with a name. Systematic botany includes both. Some people's interest in systematic botany is satisfied
by a knowledge of the local flora and an ability to identify it, an interest that has been widened by automobile travel. This is but
a limited aspect of a large subject. Important work in this field
is the building of great herbaria with specimens from all over the
A world classified chiefly by comparative morphology.
newer
taxonomic outlook is the study of the progress of evolution
through experimental work, by crossing plants of different
degrees of relationship, studying the products under different environmental conditions, and noting their establishment as new
species or subspecies or their failure to survive for genetic or
ecological reasons. The modern systematic botanist, if he is to go far in his
profession, needs a good background in general botany, cytology, genetics, ecology, plant geography, and paleobotany; otherwise, he can only collect, name, preserve, and catalogue plants, without understanding their origin. This is all the amateur systematists and some professionals attempt to do.
Obviously the students of systematic botany need to devote years of time to the subject, and teachers are much at variance
as to the sequence in which the different topics should be presented. The trend, however, is toward having classes in the first course become familiar with as many plants as possible, know
the principles involved, and receive an introduction to the newer experimental methods of geneticists and ecologists, which are not
yet well enough established to be presented in dogmatic form.
Advanced courses in systematic botany should keep in close
touch with research in all related fields.
A TEXTBOOK OF SYSTEMATIC BOTANY INTRODUCTION Modern systematic botany holds a unique position. It is in itself a science with its own ideals and its own rules and principles. The orderly classification of the wealth of vegetation that adorns the earth, a terminology understood by all nations, an application of the laws of evolution these things in themselves are worthy of man's best efforts. It has, however, another service to perform. It must aid those in other fields of endeavor, who make use of plants for many purposes, to know the identity of the kinds they use and their relationships to others. Nomenclature deals with names, which may or may not indicate relationships. Taxonomy seeks to group plants on a basis of similarities and differences, these being, as we now believe, expressions of actual phylogenetic relationships "blood rela- tionships" as we say of the higher animals. We might conceiv- ably have names without classification, but we can scarcely have classification without names. Indeed, names are necessary in almost any kind of discussion. Particularly close is the relationship between systematic botany and ecology. Names have little interest in themselves. It is only when attached to objects of study that names become significant. The out-of-door botanist not only names the plants but also notes their distribution, environment, seasonal development, and characters suggestive of economic value. EARLY BOTANICAL WORK IN AMERICA In America the development of botany in all its aspects has been an interesting one. The first distinguished American botanist was John Torrey, who, after graduating from the College of Physicians and Surgeons in New York, found greater interest in plants than in medicine and became New York State Botanist in 1
2
A TEXTBOOK OF SYSTEMATIC BOTANY
- He established two journals, the Flora of the State of New
York
and
Flora
of
North
America ,
and
helped
to
start
the
young
Asa Gray on his career in botany. The Torrey Botanical Club
with its two publications, the Journal of the Torrey Botanical Club
and the Torrey Botanical Club Memoirs, testifies to the great
esteem in which he was held by the younger botanists of his time. America's great pioneer systematic botanist, Asa Gray, after graduating in medicine and gaining an inspiration and much botanical knowledge from John Torrey, studied for a time with the more experienced botanists of England and returned to this country, where he was made Professor of Natural History at Harvard University, a position that he held up to the time of his death in 1888. He found in this country a veritable paradise, a vast and little-explored region with many familiar forms and not a few that were new to science. His tireless efforts, boundless enthusiasm, keen discrimination, and sympathetic attitude endeared him to his students and associates. It is little wonder
that his modest laboratories became a Mecca for American bota-
nists, both professional and amateur. Gray's influence was far-reaching, especially as it came during a period when many were becoming interested in work on the flora of this new country. In colleges and universities the taxonomic aspect of botany became almost an obsession. The
making of herbaria dominated botanical departments. Dr. Gray had sought to have centered at Harvard University a well-
balanced series of courses in botany, including morphology and
physiology, but the general enthusiasm ran irresistibly into the taxonomic field. As a result, many in the next generation of botanists used and taught this branch almost to the exclusion of others. This was quite unfortunate, for the impression was given that the chief purpose of botany was to collect and name plants. Indeed, in the minds of many people botany meant noth-
ing else. Such an objective alone could hardly meet the approval of the masses, and botany lost favor accordingly. Appropria- tions were grudgingly given, and many students resented the courses where the practical value was not obvious. Fortunately, America produced a few great men who, in addition to being dis- tinguished systematic botanists, had a broad outlook on the entire field of botany and were truly inspiring teachers. The strenuous efforts of Charles E, Bessey, W. A, Kellerman, W. G. Farlow,
INTRODUCTION John M. Coulter, and others soon restored the balance of emphasis in the colleges, and, indeed, the pendulum again swung too far. Many of the herbaria were stored away, classification ceased to be taught, and hundreds of students graduated from botanical courses without knowing the names of even a score of plants and without ever having attempted to use an analytical key. The layman, however, moving more slowly, continued to believe that botany had its beginning and end in nomenclature.
FIG. 1. Asa Gray (1810-1899). Great pioneer systematist of Harvard University and inspiration to many American botanists. (Courtesy of Alfred Gundersen, Brooklyn Botanic Garden.)
FIG. 2. John M. Coulter (1851-
- . Systematist and morphologist,
and inspirational teacher. For 30
years head of the department of
botany in the University of Chicago. He was highly instrumental in estab-
lishing botany in America on a broad
basis. (Courtesy of Alfred Gundersen,
Brooklyn Botanic Garden.)
r
Systematic botany in this country has now found its proper place with the other branches of botanical science. It has its highly trained specialists, most botanical students include it in their curricula, and the amateur finds in it his chief source of delight. Fortunately, the antiquated methods of teaching systematic botany by the apprentice method are being replaced by the more modern ones using lectures, laboratory work, and field trips and grounding the student in the principles of taxonomy and the
4
A TEXTBOOK OF SYSTEMATIC BOTANY
rules of nomenclature that have made botanical science as a whole a subject of respect. PURPOSES OF SYSTEMATIC BOTANY The absolute dependence of man upon plants, the many kinds that he uses, and the varied purposes he finds for them have long made the necessity for plant names of some kind imperative. To primitive peoples, who were content to apply some kind of name to only those species that were especially useful, harmful, or interesting, and who traveled but little, relationships of species were rarely thought of. Just a few simple names served every purpose. However, the application of scientific thinking to considerations other than economic called for a more orderly procedure. It should be clearly understood at the outset that the study of systematic botany involves two major procedures: (1) the estab- lishing of the relationships that exist naturally between many groups of plants, and (2) the giving of names, common or scientific or both, to all groups or kinds of plants. The first is called taxonomy and the second nomenclature. The scientific mind is not content with names alone. If we study any group of objects, from atoms to heavenly bodies, we inevitably endeavor to classify the members of the group. This orderly arrangement is the first step in scientific treatment. The systematic botanist finds about him millions of individual plants. No two are exactly alike, yet some are nearly so, while others are so different that they show scarcely any bond of rela- tionship. By noting and comparing the similarities and differ- ences, the makers of this science have brought out of chaos a fairjy orderly system. Thus a profession has been set up in which the specialist, by establishing names and descriptions of thousands of specimens, performs a service to all who deal with plants. He determines their group relationships, their distribution, properties, and other points of interest. Systematic botany forms a groundwork for all sciences dealing with plants. The myriad uses of plants make it necessary for many people who are not taxonomic specialists to have some knowledge of plant names and classifications. When we consider that green plants offer the greatest means of utilizing energy from the sun, that plants directly or indirectly furnish most of our food, cloth-
INTRODUCTION
5
ing, shelter, fuel, medicine, paper, decorative materials, and many other useful things, we are made to realize that an orderly classifi- cation of them, understood in some measure by all civilized people, does much to prevent confusion and to facilitate cooper- ative effort.
Forestry. Very extensive use of systematic botany is made in forestry. Every kind of tree must be named and classified, and its characteristics, distribution, and abundance must be learned. But forestry is not limited to the production of lumber. The national forests are extensively used for the grazing of livestock; and those who control the leasing and use of forest lands for this purpose must be familiar with all forms of vegetation and must know the palatability and food value of each kind, its methods of propagation, and the amount of grazing it will stand without danger of depletion. Furthermore, increasing use is made of the forests for recreational purposes, and national parks and forestry services are publishing splendid bulletins, some with beautiful illustrations, on the plants and shrubs that are most attractive to
visitors.
Agriculture, Horticulture, and Floriculture. In the broad field of plant breeding extensive progress has been made in recent years
in the securing of improved varieties of grains, fruits, flowers, etc. This is not accomplished by haphazard tests but follows definite procedures. Crossing is usually involved, and a knowledge of species and varieties from a world standpoint is required to secure suitable stocks for the purpose. Even varieties resistant to diseases that can be controlled by no other method have been secured in this way. Foreign seed and plant introduction is done mostly by men well versed in systematic botany. Range Management. As the years go by, the American people are becoming more conscious of the fact that our once fertile lands, both wooded and prairie, are being exploited to a point where erosion and dust blowing, added to a depletion of humus
and of inorganic food materials especially nitrates, phosphates,
and potash by cropping have become national problems.
Courses in range management are being established that make
We more study of plant life than of livestock.
are coming to
realize that the conservation of native grasses and other plants
and the selection of species best suited for holding the soil call for
the efforts of ecologists who are well trained in systematic
6
A TEXTBOOK OF SYSTEMATIC BOTANY
botany. Indeed, forestry and range management furnish the greatest practical application of this branch of botanical science. Ecology. The character of the vegetation has long been known as a valuable index of soil conditions. Certain species are definitely hydrophytic, xerophytic, or halophytic, and soil characters of all kinds may be indicated by the vegetation growing on the surface. In many cases good ecologists can quickly interpret the character of a land area by its vegetation, with little or no study of the soil itself. The plant ecologist must be a close student of systematic botany, knowing both the names of plants and their relationships, for his conclusions with regard to the effects of environment and the succession of species on an area would be wholly misleading if applied to species or groups different from the ones specified. The helpfulness of systematic botany and ecology is mutual, for, as explained later, a wholly new conception of plant species and their evolutionary origin is coming from a combination of genetic and ecological studies made by crossing related plants and studying the resulting products. Paleobotany. One of our greatest difficulties in tracing relationships of plants and animals is that the ancestral forms connecting existing species have disappeared. The scattering fossils that are found here and there, though presenting a fragmentary picture, are very useful in revealing the characters of these ances- tral forms and have real significance to those who have for a background a knowledge of taxonomy. Much of the research in taxonomy is concerned with piecing together the discoveries in paleontology, genetics, cytology, and other branches of science into a working plan of classification. In many groups classification has proceeded only far enough to associate certain forms of life that have a kind of resemblance that may or may not represent actual relationship. The systematic botanist has not yet reached the place where he can afford to be static. His classification must be flexible and frequently revised to embody new information and to adjust itself to the newer view- points. If he takes this progressive attitude he can be of tremendous service in summarizing and utilizing the discoveries of investigators in related fields. He has a duty beyond the mere naming of plants. From the foregoing it will be seen that collecting the flowering
INTRODUCTION
7
plants of a limited region and learning their names is but a simple and superficial part of the science of systematic botany. Amateur Botany. With the growth of the different sciences there is a desire on the part of many people to study them from the amateur's standpoint. Probably no other science, except possibly geology, has so captured the interest of the amateur as botany. Such studies could be made in any field of this science, but systematic botany is the one with the greatest appeal. This is largely due to the fact that it gives an opportunity for satisfying the human desire to collect. While some amateur collections of plants serve only a temporary purpose, others are of great value and contain thousands of specimens accompanied by important ecological data. Usually such collections are finally donated to educational institutions where they will be protected from fire and other destructive agencies. More and more the spirit of service is pervading the scientific world. With increasing effectiveness representative men in each science will apply their work and that of their colleagues to everyday life. In harmony with this tendency, the systematic botanist of tomorrow will add to the names and classification of plants much information of value to the human race.