Part 17

520. Plants and animals have two great peculiarities: 1st, they form themselves; and 2d, they multiply themselves. They reproduce their kind in a continued succession of

521. =Individuals.= Mineral things occur as _masses_, which are divisible into smaller and still smaller ones without alteration of properties. But organic things (vegetables and animals) exist as _individual beings_. Each owes its existence to a parent, and produces similar individuals in its turn. So each individual is a link of a chain; and to this chain the natural-historian applies the name of

522. =Species.= All the descendants from the same stock therefore compose one species. And it was from our observing that the several sorts of plants or animals steadily reproduce themselves, or, in other words, keep up a succession of similar individuals, that the idea of species originated. There are few species, however, in which man has actually observed the succession for many generations. It could seldom be proved that all the White Pine trees or White Oaks of any forest came from the same stock. But observation having familiarized us with the general fact that individuals proceeding from the same stock are essentially alike, we infer from their close resemblance that these similar individuals belong to the same species. That is, we infer it when the individuals are as much like each other as those are which we know, or confidently suppose, to have sprung from the same stock.

523. Identity in species is inferred from close similarity in all essential respects, or whenever the differences, however considerable, are not known or reasonably supposed to have been originated in the course of time under changed conditions. No two individuals are exactly alike; a tendency to variation pervades all living things. In cultivation, where variations are looked after and cared for, very striking differences come to light; and if in wild nature they are less common or less conspicuous, it is partly because they are uncared for. When such variant forms are pretty well marked they are called

524. =Varieties.= The White Oak, for example, presents two or three varieties in the shape of the leaves, although they may be all alike upon each particular tree. The question often arises, and it is often hard to answer, whether the difference in a particular case is that of a variety, or is specific. If the former, it may commonly be proved by finding such intermediate degrees of difference in various individuals as to show that no clear distinction can be drawn between them; or else by observing the variety to vary back again in some of its offspring. The sorts of Apples, Pears, Potatoes, and the like, show that differences which are permanent in the individual, and continue unchanged through a long series of generations when propagated by division (as by offsets, cuttings, grafts, bulbs, tubers, etc.), are not likely to be reproduced by seed. Still they sometimes are so, and perhaps always tend in that direction. For the fundamental law in organic nature is that offspring shall be like parent.

RACES are such strongly marked varieties, capable of coming true to seed. The different sorts of Wheat, Maize, Peas, Radishes, etc., are familiar examples. By selecting those individuals of a species which have developed or inherited any desirable peculiarity, keeping them from mingling with their less promising brethren, and selecting again the most promising plants raised from their seeds, the cultivator may in a few generations render almost any variety transmissible by seed, so long as it is cared for and kept apart. In fact, this is the way the cultivated domesticated races, so useful to man, have been fixed and preserved. Races, in fact, can hardly, if at all, be said to exist independently of man. But man does not really produce them. Such peculiarities--often surprising enough--now and then originate, we know not how (the plant _sports_, as the gardeners say); they are only preserved, propagated, and generally further developed, by the cultivator's skilful care. If left alone, they are likely to dwindle and perish, or else revert to the original form of the species. Vegetable races are commonly annuals, which can be kept up only by seed, or herbs of which a succession of generations can be had every year or two, and so the education by selection be completed without great lapse of time. But all fruit-trees could probably be fixed into races in an equal number of generations.

BUD-VARIETIES are those which spring from buds instead of seed. They are uncommon to any marked extent. They are sometimes called _Sports_, but this name is equally applied to variations among seedlings.

CROSS-BREEDS, strictly so-called, are the variations which come from cross-fertilizing one variety of a species with another.

HYBRIDS are the varieties, if they may be so called,--which come from the crossing of species (331). Only nearly related species can be hybridized; and the resulting progeny is usually self-sterile, but not always. Hybrid plants, however, may often be fertilized and made prolific by the pollen of one or the other parent. This produces another kind of cross-breeds.

525. Species are the units in classification. Varieties, although of utmost importance in cultivation and of considerable consequence in the flora of any country, are of less botanical significance. For they are apt to be indefinite and to shade off one form into another. But species, the botanist _expects_ to be distinct. Indeed, the practical difference to the botanist between species and varieties is the definite limitation of the one and the indefiniteness of the other. The botanist's determination is partly a matter of observation, partly of judgment.

526. In an enlarged view, varieties may be incipient species; and nearly related species probably came from a common stock in earlier times. For there is every reason to believe that existing vegetation came from the more or less changed vegetation of a preceding geological era. However that may be, species are regarded as permanent and essentially unchanged in their succession of individuals through the actual ages.

527. There are, at nearly the lowest computation, as many as one hundred thousand species of phanerogamous plants, and the cryptogamous species are thought to be still more numerous. They are all connected by resemblances or relationships, near and remote, which show that they are all parts of one system, realizations in nature, as we may affirm, of the conception of One Mind. As we survey them, they do not form a single and connected chain, stretching from the lowest to the highest organized species, although there obviously are lower and higher grades. But the species throughout group themselves, as it were, into clusters or constellations, and these into still more comprehensive clusters, and so on, with gaps between. It is this clustering which is the ground of the recognition of _kinds_ of species, that is, of groups of species of successive grades or degree of generality; such as that of similar species into _Genera_, of genera into _Families_ or _Orders_, of orders into _Classes_. In classification the sequence, proceeding from higher or more general to lower or special, is always CLASS, ORDER, GENUS, SPECIES, VARIETY (if need be).

528. =Genera= (in the singular, _Genus_) are assemblages of closely related species, in which the essential parts are all constructed on the same particular type or plan. White Oak, Red Oak, Scarlet Oak, Live Oak, etc., are so many species of the Oak genus (Latin, _Quercus_). The Chestnuts compose another genus; the Beeches another. The Apple, Pear, and Crab are species of one genus, the Quince represents another, the various species of Hawthorn a third. In the animal kingdom the common cat, the wild-cat, the panther, the tiger, the leopard, and the lion are species of the cat kind or genus; while the dog, the jackal, the different species of wolf, and the foxes, compose another genus. Some genera are represented by a vast number of species, others by few, very many by only one known species. For the genus may be as perfectly represented in one species as in several, although, if this were the case throughout, genera and species would of course be identical. The Beech genus and the Chestnut genus would be just as distinct from the Oak genus even if but one Beech and Chestnut were known; as indeed was once the case.

529. =Orders= are groups of genera that resemble each other; that is, they are to genera what genera are to species. As familiar illustrations, the Oak, Chestnut, and Beech genera, along with the Hazel genus and the Hornbeams, all belong to one order. The Birches and the Alders make another; the Poplars and Willows, another; the Walnuts (with the Butternut) and the Hickories, still another. The Apple genus, the Quince and the Hawthorns, along with the Plums and Cherries and the Peach, the Raspberry with the Blackberry, the Strawberry, the Rose, belong to a large order, which takes its name from the Rose. Most botanists use the names "Order" and "Family" synonymously; the latter more popularly, as "the Rose Family," the former more technically, as "Order _Rosaceae_."

530. But when the two are distinguished, as is common in zoology, Family is of lower grade than Order.

531. =Classes= are still more comprehensive assemblages, or great groups. Thus, in modern botany, the Dicotyledonous plants compose one class, the Monocotyledonous plants another (36-40).

532. These four grades, Class, Order, Genus, Species, are of universal use. Variety comes in upon occasion. For, although a species may have no recognized varieties, a genus implies at least one species belonging to it; every genus is of some order, and every order of some class.

533. But these grades by no means exhaust the resources of classification, nor suffice for the elucidation of all the distinctions which botanists recognize. In the first place, a higher grade than that of class is needful for the most comprehensive of divisions, that of all plants into the two _Series_ of Phanerogamous and Cryptogamous (6); and in natural history there are the two _Kingdoms_ or _Realms_, the Vegetable and the Animal.

534. Moreover, the stages of the scaffolding have been variously extended, as required, by the recognition of assemblages lower than class but higher than order, viz. _Subclass_ and _Cohort_; or lower than order, a _Suborder_; or between this and genus, a _Tribe_; or between this and tribe, a _Subtribe_; or between genus and species, a _Subgenus_; and by some a species has been divided into _Subspecies_, and a variety into _Subvarieties_. Last of all are _Individuals_. Suffice it to remember that the following are the principal grades in classification, with the proper sequence; also that only those here printed in small capitals are fundamental and universal in botany:--

SERIES, CLASS, Subclass, Cohort, ORDER, or FAMILY, Suborder, Tribe, Subtribe, GENUS, Subgenus or Section, SPECIES, Variety.

Sec. 2. NAMES, TERMS, AND CHARACTERS.

535. The name of a plant is the name of its genus followed by that of the species. The name of the genus answers to the surname (or family name); that of the species to the baptismal name of a person. Thus _Quercus_ is the name of the Oak genus; _Quercus alba_, that of the White Oak, _Q. rubra_, that of Red Oak, _Q. nigra_, that of the Black-Jack, etc. Botanical names being Latin or Latinized, the adjective name of the species comes after that of the genus.

536. =Names of Genera= are of one word, a substantive. The older ones are mostly classical Latin, or Greek adopted into Latin; such as _Quercus_ for the Oak genus, _Fagus_ for the Beech, _Corylus_, the Hazel, and the like. But as more genera became known, botanists had new names to make or borrow. Many are named from some appearance or property of the flowers, leaves, or other parts of the plant. To take a few examples from the early pages of the "Manual of the Botany of the Northern United States,"--the genus _Hepatica_ comes from the shape of the leaf, resembling that of the liver. _Myosurus_ means mouse-tail. _Delphinium_ is from delphin, a dolphin, and alludes to the shape of the flower, which was thought to resemble the classical figures of the dolphin. _Xanthorrhiza_ is from two Greek words meaning yellow-root, the common name of the plant. _Cimicifuga_ is formed of two Latin words meaning to drive away bugs, i. e. Bugbane, the Siberian species being used to keep away such vermin. _Sanguinaria_, the Bloodroot, is named from the blood-like color of its juice. Other genera are dedicated to distinguished botanists or promoters of science, and bear their names: such are _Magnolia_, which commemorates the early French botanist, Magnol; and _Jeffersonia_, named after President Jefferson, who sent the first exploring expedition over the Rocky Mountains. Others bear the name of the discoverer of the plant; as, _Sarracenia_, dedicated to Dr. Sarrazin, of Quebec, who was one of the first to send the common Pitcher-plant to the botanists of Europe; and _Claytonia_, first made known by the early Virginian botanist Clayton.

537. =Names of Species.= The name of a species is also a single word, appended to that of the genus. It is commonly an adjective, and therefore agrees with the generic name in case, gender, etc. Sometimes it relates to the country the species inhabits; as, Claytonia _Virginica_, first made known from Virginia; Sanguinaria _Canadensis_, from Canada, etc. More commonly it denotes some obvious or characteristic trait of the species; as, for example, in Sarracenia, our northern species is named _purpurea_, from the purple blossoms, while a more southern one is named _flava_, because its petals are yellow; the species of Jeffersonia is called _diphylla_, meaning two-leaved, because its leaf is divided into two leaflets. Some species are named after the discoverer, or in compliment to a botanist who has made them known; as, Magnolia _Fraseri_, named after the botanist Fraser, one of the first to find this species; and Sarracenia _Drummondii_, for a Pitcher-plant found by Mr. Drummond in Florida. Such personal specific names are of course written with a capital initial letter. Occasionally some old substantive name is used for the species; as Magnolia _Umbrella_, the Umbrella tree, and Ranunculus _Flammula_. These are also written with a capital initial, and need not accord with the generic name in gender. Geographical specific names, such as _Canadensis_, _Caroliniana_, _Americana_, in the later usage are by some written without a capital initial, but the older usage is better, or at least more accordant with English orthography.

538. =Varietal Names=, when any are required, are made on the plan of specific names, and follow these, with the prefix _var_. Ranunculus Flammula, var. _reptans_, the creeping variety: R. abortivus, var. _micranthus_, the small-flowered variety of the species.

539. In recording the name of a plant it is usual to append the name, or an abbreviation of the name, of the botanist who first published it; and in a flora or other systematic work, this reference to the source of the name is completed by a further citation of the name of the book, the volume and page where it was first published. So "_Ranunculus acris_, L.," means that this Buttercup was first so named and described by Linnaeus; "_R. multifidus_, Pursh," that this species was so named and published by Pursh. The suffix is no part of the name, but is an abbreviated reference, to be added or omitted as convenience or definiteness may require. The authority for a generic name is similarly recorded. Thus, "_Ranunculus_, L.," means that the genus was so named by Linnaeus; "_Myosurus_, Dill.," that the Mouse-tail was established as a genus under this name by Dillenius; _Caulophyllum_, Michx., that the Blue Cohosh was published under this name by Michaux. The full reference in the last-named instance would be, "in Flora Boreali-Americana, first volume, 205th page,"--in the customary abbreviation, "Michx. Fl. i. 205."

540. =Names of Orders= are given in the plural number, and are commonly formed by prolonging the name of a genus of the group taken as a representative of it. For example, the order of which the Buttercup or Crowfoot genus, _Ranunculus_, is the representative, takes from it the name of _Ranunculaceae_; meaning _Plantae Ranunculaceae_ when written out in full, that is, Ranunculaceous Plants. Some old descriptive names of orders are kept up, such as _Cruciferae_ for the order to which Cress and Mustard belong, from the cruciform appearance of their expanded corolla, and _Umbelliferae_, from the flowers being in umbels.

541. =Names of Tribes=, also of suborders, subtribes, and the like, are plurals of the name of the typical genus, less prolonged, usually in _eae_, _ineae_, _ideae_, etc. Thus the proper Buttercup tribe is _Ranunculeae_, of the Clematis tribe, _Clematideae_. While the Rose family is _Rosaceae_, the special Rose tribe is _Roseae_.

542. =Names of Classes, etc.= For these see the following synopsis of the actual classification adopted, p. 183.

543. So a plant is named in two words, the generic and the specific names, to which may be added a third, that of the variety, upon occasion. The generic name is peculiar: obviously it must not be used twice over in botany. The specific name must not be used twice over in the same genus, but is free for any other genus. A _Quercus alba_, or White Oak, is no hindrance to _Betula alba_, or White Birch; and so of other names.

544. =Characters and Descriptions.= Plants are _characterized_ by a terse statement, in botanical terms, of their peculiarities or distinguishing marks. The character of the order should include nothing which is common to the whole class it belongs to; that of the genus, nothing which is common to the order; that of the species nothing which is shared with all other species of the genus; and so of other divisions. _Descriptions_ may enter into complete details of the whole structure.

545. =Terminology=, also called _Glossology_, is nomenclature applied to organs or parts, and their forms or modifications. Each organ or special part has a substantive name of its own: shapes and other modifications of an organ or part are designated by adjective terms, or, when the forms are peculiar, substantive names are given to them. By the correct use of such botanical terms, and by proper subordination of the characters under the order, genus, species, etc., plants may be described and determined with much precision. The classical language of botany is Latin. While modern languages have their own names and terms, these usually lack the precision of the Latin or Latinized botanical terminology. Fortunately, this Latinized terminology has been largely adopted and incorporated into the English technical language of botany, thus securing precision. And these terms are largely the basis of specific names of plants.

546. A glossary or vocabulary of the principal botanical terms used in phanerogamous and vascular cryptogamous botany is appended to this volume, to which the student may refer, as occasion arises.

Sec. 3. SYSTEM.

547. Two systems of classification used to be recognized in botany,--the artificial and the natural; but only the latter is now thought to deserve the name of a system.

548. Artificial classifications have for object merely the ascertaining of the name and place of a plant. They do not attempt to express relationships, but serve as a kind of dictionary. They distribute the genera and species according to some one peculiarity or set of peculiarities (just as a dictionary distributes words according to their first letters), disregarding all other considerations. At present an artificial classification in botany is needed only as a key to the natural orders,--as an aid in referring an unknown plant to its proper family; and such keys are still very needful, at least for the beginner. Formerly, when the orders themselves were not clearly made out, an artificial classification was required to lead the student down to the genus. Two such classifications were long in vogue: First, that of Tournefort, founded mainly on the leaves of the flower, the calyx and corolla: this was the prevalent system throughout the first half of the eighteenth century; but it has long since gone by. It was succeeded by the well-known

549. =Artificial System of Linnaeus=, which was founded on the stamens and pistils. It consists of twenty-four classes, and of a variable number of orders; the classes founded mainly on the number and disposition of the stamens; the orders partly upon the number of styles or stigmas, partly upon other considerations. Useful and popular as this system was down to a time within the memory of still surviving botanists, it is now completely obsolete. But the tradition of it survives in the names of its classes, Monandria, Diandria, Triandria, etc., which are familiar in terminology in the adjective terms monandrous, diandrous, triandrous, etc. (284); also of the orders, Monogynia, Digynia, Trigynia, etc., preserved in the form of monogynous, digynous, trigynous, etc. (301); and in the name Cryptogamia, that of the 24th class, which is continued for the lower series in the natural classification.

550. =Natural System.= A genuine system of botany consists of the orders or families, duly arranged under their classes, and having the tribes, the genera, and the species arranged in them according to their relationships. This, when properly carried out, is the _Natural System_; because it is intended to express, as well as possible, the various degrees of relationship among plants, as presented in nature; that is, to rank those species and those genera, etc., next to each other in the classification which are really most alike in all respects, or, in other words, which are constructed most nearly on the same particular plan.

551. There can be only _one_ natural system of botany, if by this term is meant the plan according to which the vegetable creation was called into being, with all its grades and diversities among the species, as well of past as of the present time. But there may be many natural systems, if we mean the attempts of men to interpret and express that plan,--systems which will vary with advancing knowledge, and with the judgment and skill of different botanists. These must all be very imperfect, bear the impress of individual minds, and be shaped by the current philosophy of the age. But the endeavor always is to make the classification answer to Nature, as far as any system can which has to be expressed in a definite and serial arrangement.

552. So, although the classes, orders, genera, etc., are natural, or as natural as the systematist can make them, their grouping or order of arrangement in a book, must necessarily be in great measure artificial. Indeed, it is quite impossible to arrange the orders, or even the few classes, in a single series, and yet have each group stand next to its nearest relatives on both sides.

553. Especially it should be understood that, although phanerogamous plants are of higher grade than cryptogamous, and angiospermous or ordinary phanerogamous higher than the gymnospermous, yet there is no culmination in the vegetable kingdom, nor any highest or lowest order of phanerogamous plants.

554. The particular system most largely used at present in the classification of the orders is essentially the following:--

SERIES I. PHANEROGAMIA: PHANEROGAMOUS OR FLOWERING PLANTS.

CLASS I. DICOTYLEDONES ANGIOSPERMEAE, called for shortness in English, DICOTYLEDONS or DICOTYLS. Ovules in a closed ovary. Embryo dicotyledonous. Stem with exogenous plan of growth. Leaves reticulate-veined,