TAXONOMY. 163 



The first thirteen of the Linnasan classes are divided into orders founded on the 

 number of ovaries or free styles composing the pistil. In monogynia the pistil is 

 formed of a single carpel, or of several carpels united into one by their ovaries and 

 styles ; in digynia there are two distinct ovaries or styles ; in trigynia three ; in tetra- 

 gynia four ; in pentagynia five ; in hexagynia six ; in polygynia any number above ten. 

 The 14th class contains two orders : gymnospermia, in which the pistil is composed 

 of four lobes simulating naked seeds ; angiospermia, in which the seeds are enclosed 

 in a capsule. The 15th class is said to be siliquose or siliculose, according as the 

 fruit is or is not three times longer than broad. The 1 6th, 17th, 18th, 20th, 21st, and 

 22nd classes have their orders founded on the number and connection of the stamens 

 and styles {triandria, pentandria, polyandria, monogynia, polygynia, monadelphia, &c.). 

 The 19th class is divided into polygamia cequales, in which all the centre flowers of 

 the capitulum hare stamens and pistils, and those of the circumference have pistils 

 and are fertile ; polygamia frustranea, where the flowers of the circumference are 

 female and sterile ; polygamia neeessaria, where the flowers of the centre are male, 

 and those of the circumference female and fertile, &c. The 23rd class is divided 

 into monoecious, dioecious, trioecious. The 24th class is divided into Ferns, Mosses, Algce, 

 and Fungi. 



A complete classification ought to satisfy two oouiditions : the first that of 

 enabling, one quickly to ascertain the name given by botanists to a plant, and to sepa- 

 rate it from the rest of the Vegetable Kingdom by differential characters, as salient 

 as possible. This object ought to be fulfilled by the system, which should be a true 

 alphabetical dictionary, facilitating research ; and its divisions ought, therefore, to be 

 established on the most apparent characters, however bizarre and dissimilar they may 

 be. From this point of view the Linnsean classification is a chef d'wuvre which will 

 perhaps never be surpassed, in spite of the inconveniences resulting from the not very 

 numerous difiiculties to be overcome in applying it. Dichotomous keys are systems 

 which consist in placing before the student a series of questions wherein the choice 

 lies between two contradictory propositions, in such a manner that, the one being 

 granted, the other must be necessarily rejected. 



The second condition is that of placing each species and genus amongst those 

 with which it agrees in the most essential points of resemblance : if this object be 

 fulfilled, the method becomes a true science, its diyisions being founded on the 

 most important organs, without regard to their number, or to the difiiculty of 

 observing them. System enables us to discover the name of an individual from 

 its description ; method enables us to ascertain its position in the Vegetable 

 Kingdom ; — method is hence the complement of system. 



The affinities which should form the basis of every natural method were first 

 established by A. L. de Jussieu. Before him, Magnol, of Montpellier, had introduced 

 into Bota,nj families of which the arrangement was founded on the structure of the 

 calyx and corolla; Rivin had published a classification based on the form of the 

 corolla, on the number of the seeds, on the form, consistency, and cells of the 

 fruit ; Bay had classed upwards of 18,000 species, which he divided according to 

 the number of cotyledons, the separation or aggregation of the flowers, the presence 



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