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superfluous, or that is common to all the species of the same genus, or to all the genera of the same order, or to all the orders of the same class. It may be said to comprehend the chief differences and resemblances of bodies. In drawing up essential characters, much discretion requires to be exercised : they may be over-short or over-long; characters of importance may be omitted, and others of no importance introduced. Hence no better evidence need be desired of the merit of a botanist than his essential characters, — from which a practised eye will readily detect both how much the author knows, and what he does not know. As models of the manner in which these should be drawn up, no book can be consulted with more advantage than the Genera Plantarum of Jussieu, in which classical elegance of language, and as much rigid botanical precision as was supposed necessary at the time the work was written, are combined in a manner that has seldom been surpassed. The defects of that work were inseparable from the state of Botany at the time it appeared; the characters of the genera and orders not embracing all those points of structure which are now known to be sential.

The following character, assigned by Brown to the order PROTEACEÆ (Prodr. Fl. N. Holl. p. 363.), may be taken as a specimen of the manner in which an essential character of the briefest kind ought to be constructed :

Perianthium tetraphyllum v. quadrifidum, æstivatione valvata. Stamina quatuor (altero nunc sterili), foliolis perianthii opposita. Ovarium unicum, liberum. Stylus simplex. Stigma subindivisum. Semen (pericarpii varii) exalbuminosum. Embryo dicotyledoneus (quandoque polycotyledoneus), rectus. Radicula infera.”

In this character enough is expressed to distinguish the order from all others; and, at the same time, by a careful suppression of all superfluous terms, it is reduced within exceedingly narrow limits. Such a character as this leaves nothing to be desired, when the essence only of a mass of characters is the object in view.

The following, from the same author, is a specimen of an essential character of AcanTHACEÆ, of a more extended kind :

Calyx 5---4-divisus, partitus v. tubulosus, æqualis v. inæqualis ; rarò multifidus v. integer et obsoletus: persistens. Corolla monopetala, hypogyna, staminifera, plerumque irregularis; limbo ringente v. bilabiato, rarò unilabiato; nunc subæqualis; decidua. Stamina sæpius duo, antherifera, modo 4 didynama, brevioribus quandoque effætis. Antheræ y. biloculares, loculis insertione inæqualibus æqualibusve; v. uniloculares; longitudinaliter dehiscentes. Ovarium disco glanduloso basi cinctum, biloculare loculis 2 polyspermis. Stylus I. Stigma bilobum, rarò indivisum. Capsula bilocularis, loculis 2 polyspermis, abortione quandoque monospermis, elasticè bivalvis. Dissepimentum contrarium, per axin (medio quandoque apertam) bipartibile, segmentis valvulis adnatis modò ab iisdem elasticè dissilientibus, integris v. rarò spontè bipartibilibus; margine interiore seminiferis. Semina processubus subulatis adscendentibus disse pimenti plerumque subtensa, subrotunda: Testa laxa. Albumen nullum. Embryo curvatus v. rectus; Cotyledones magnæ, suborbiculatæ; Radicula teres, descendens, et simul centripeta, curvata v. recta ; Plumula inconspicua. -—_ Herba v. Frutices, intra tropicos præcipuè provenientes ; pube, dum adsit, simplici, nunc capitatâ, rarissimè stellatâ. Folia opposita, rarò quaterna, exstipulata, simplicia, indivisa, integra v. serrata ; rarò sinuata v. sublobata. Inflorescentia terminalis v. axillaris, spicata, racemosa, fasciculata, paniculata v. solitaria. Flores in spicis sæpius oppositi, nunc alterni, tribracteati, bracteis lateralibus rarò deficientibus, quandoque magnis foliaceis calycem nanum, interdum obsoletum, includentibus."

In this instance a much greater number of particulars is introduced than in the former; but still it comprehends nothing like all the characters that would be included in a general description.

The following is also a specimen of a generic and specific character from the same author. It shows the plan upon which the essential characters of genera should be constructed: —

« VERONICA L., Juss.

66 Hebe Juss. Calyx 4-partitus, rarò 5-partitus.

Corolla subrotata ;

Tubus calyce brevior; Limbus 4-partitus, inæqualis, lobis indivisis. Stamina 2, antherifera, sterilia nulla. Capsula valvis medio septiferis v. bipartibilis, Herbæ v. Frutices. Folia opposita, quandoque verticillata, v, alterna, sæpe dentata v. incisa. Inflorescentia varia. Calyces ebracteati,

“$ 1. Capsula bipartibilis. “ 1. V. formosa, fruticosa, foliis perennantibus decussatis lanceolatis integerrimis glaberrimis basi acutis, ramis bifariam pilosiusculis, corymbis axillaribus paucifloris.” (Prodr. 434.)

In these characters it is difficult to say which is most to be admired, the skill with which every thing superfluous is retrenched, or the ingenuity with which every thing essential is introduced. Nothing that is general to the order is introduced into the generic character; and nothing that the generic character comprehends is discoverable in the specific. By making the peculiarity of Capsula bipartibilis the distinction of a section, the necessity of introducing that circumstance into the specific characters of any of the species comprehended in the section is avoided.

Compare with this the following generic and specific characters taken from Labillardière's Sertum Austro-Caledoni

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“ MICROSEMMA; a genus of Ternströmiaceæ (?). Calyx 5-phyllus, rarè 6-phyllus, persistens, foliolis tribus interioribus. Coronula petaloidea, petalis 10-12 distinctis.

Stamina numerosa (30 circiter), hypogina, filamentis inter se basi subconnatis, antheris bilocularibus reniformibus. Germen globulosum, superum, stylo simplici, stigmate 5-6-fido. Capsula ovata, 10-12-locularis, valvis medio septiferis, 10—12valvis. Semina solitaria, in summo valvularum intûs affixa, perispermo carnoso, radiculâ superâ.” (p. 58.)

Upon this character it may be observed, that the calyx is described awkwardly, and at a greater expense of words than is necessary: if he had said, calyx 5-6-phyllus imbricatus, the same idea would have been expressed : rarè should be rarò. In the next place, “coronula petaloidea" is a bad term, conveying no precise notion of the organ it is intended to designate. What is a coronula? If it is a row of petals, why call it otherwise ? And it appears to be so, because it is immediately afterwards described as consisting of 10-12 distinct petals. In the next sentence, hypogina is misspelt ; and the anthers are said to be bilocular and reniform, a character by no means essential ; while their being covered with glandular dots, and the mode of their attachment to the filament, both of which should have been introduced, are omitted. Again, the germen, meaning the ovary, is said to be globulose: what is globulose? Is it bullet-shaped, or round and small? If the former, the term is inapplicable; if the latter, the meaning is not expressed: it probably was intended for

subglobose.” The capsule is said to be ovate, a quality of no consequence if it existed ; but not true, inasmuch as it appears from the figure to be round. The construction of what follows is what we call in English putting the cart before the horse : instead of “ valvis medio septiferis 10—12 valvis," it shonld have been, “10-12 valvis, valvis medio septiferis ;” and all that is said about the attachment of the seeds might have been better expressed by two words,“ semina pendula.” It is said that they are attached to the top of the valves, in the inside: did any one ever hear of seeds being attached to the outside ? Let the character be properly cut down, and see what remains of it.

MICROSEMMA. “ Sepala 5—6, imbricata, persistentia. Petala 10—12. Stamina numerosa, hypogyna, submonadelpha : antheris bilocularibus. Ovarium superum; stylus simplex; stigmata 5-6. Capsula 10—12-locularis, valvis totidem loculicidis ; semina solitaria pendula ; albumen carnosum; radicula supera.”

But it is not in inaccuracy of language alone, or in the misplacing the members of a sentence, that an essential character may be defective: it may be expressed with a good selection of terms, and a due attention to arrangement; but the terms may be wrongly applied, or important characters may be omitted, or the author may not understand the structure of what he is describing. Take, as an instance, the following character of Carex, by the late Sir James Smith:

Barren flowers numerous, aggregate, in one, or more, oblong, dense catkins ; their scales imbricated every way. Calyx a single, lanceolate, undivided, permanent scale to each floret. Corolla none. Filaments 3, rarely fewer, capillary, erect or drooping, longer than the scales. Anthers vertical, long, linear, of 2 cells.

Fertile flowers numerous, in the same, or more usually in a different, catkin, very rarely on a separate plant. Calyx as in the barren flower. Corolla a single, hollow, compressed, ribbed, often angular, permanent glume to each floret; contracted, mostly cloven, and often elongated at the extremity. Germen superior, roundish; with three, rarely but two, angles, very smooth. Style one, terminal, cylindrical, short. Stigmas three, more rarely two only, awl-shaped, long, tapering, downy, deciduous. Seed the shape of the germen, with unequal angles, loosely coated with the enlarged, either hardened or membranous, permanent corolla, both together constituting the fruit."

This character is carefully written, but full of inaccurate and confused applications of terms. The term catkin should be spike; for a catkin is deciduous, a spike persistent: and the inflorescence in Carex is of the latter kind. In the next place, what is called the calyx is a bract. What is called the corolla of the fertile flowers is two confluent bracts; and, therefore, not a single glume, but a double one. Finally, what is called the seed is the pericarp: in the young state it is called the germen, which is equivalent to ovary; but, by the time the ovary is ripe, it is metamorphosed into a seed.

Inaccuracies of this kind not only disfigure botanical writings, but very often lead the inexperienced botanist into errors and misconceptions.

In constructing essential and differential characters, it is customary to use the nominative case for genera and orders, and the ablative for species; but in English the nominative only is employed in both cases.

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