572 LECTURE LVIII. 



been omitted by some late botanists ; here the filaments are fixed on the 

 pistil ; or more properly, in the arums, within the pistils. The three fol- 

 lowing classes, monoecia, dioecia, and polygamia, differ from the rest in 

 having some flowers with filaments or chives, and some with pistils only, 

 either on the same plant, or on different plants, or mixed with flowers of 

 the more common construction. Most of the forest trees belong to these 

 classes, but the distinctions which separate them from other classes are not 

 always very uniformly preserved, and, for this reason, many later botanists 

 have disused them. The plants of the last class, cryptogamia, are exceed- 

 ingly numerous ; the families of ferns, mosses, algae, or membranous weeds, 

 and fungi or mushrooms, fill up its extensive departments ; some have also 

 separated a part of the algae under the name of hepaticae, or gelatinous 

 weeds. In this class the fructifications are extremely various ; some of 

 the fuci and confervae approach so much in their general appearance and 

 mode of growth to corallines and zoophytes, that they seem to form an 

 obvious connexion between the lowest ranks of the vegetable and animal 

 kingdoms ; while other plants of the class are scarcely distinguishable by 

 their appearance from some of the productions of the mineral kingdom. 



The French have introduced into very general use the botanical system 

 of Jussieu. The most prominent feature in this system is the division of 

 all the genera into a hundred natural orders, which are also arranged in 

 fifteen classes. Jussieu begins, like Linne, with the separation of crypto- 

 gamic from phanerogamic plants; the seeds of the cryptogamic plants, 

 which form the first class, being without cotyledons or seed leaves, and all 

 other plants being distinguished into such as have seeds with one and with 

 two cotyledons. Accordingly as the stamina or filaments are inserted 

 below the pistil, on the calyx, or on the seed vessel, the first description of 

 seeds affords three distinct classes. The plants which have two cotyledons 

 follow, and are divided into apetalous, monopetalous, and polypetalous, 

 from distinctions respecting the corolla or flower leaves, which are some- 

 what arbitrarily understood ; and lastly diclinous, from the separation of 

 the stamina and pistils. The three first of these divisions are subdivided 

 according to the insertion of the stamina, and the union or separation of 

 the antherae, which they support, into ten classes, making, with the four 

 already mentioned, fourteen, to which the diclinous plants add a fifteenth. 

 The orders are determined without any particular limitation of the parts 

 from which the characters are taken. This system is of acknowledged 

 merit as a philosophical classification of the natural orders of plants ; 

 such vegetables as nearly agree in their habits and appearances being 

 brought more uniformly together than in the system of Linne. Hence, 

 in the arrangement of a botanical garden, or in a treatise on the chemical 

 or medical properties of plants, it might be employed with advantage : but 

 for the practical purposes of botanical investigation it appears to be utterly 

 unfit, since its author has sacrificed all logical and systematical laws 

 to the attempt to follow nature, in analogies, which are often discoverable 

 only with great difficulty, and which are seldom reducible to methodical 

 definitions. 



