130 CHARACTERS USED IN CLASSIFICATION. 



in their structure, exogenous in their mode of growth, and their leaves 

 are distinguished by branching;, reticulate veins. 



Comparison of the Methods of Tourne/ort, lAnncBUSy and Jussieu. 



We have now presented the pupil with the outlines of three modes 

 of classification, exhibiting the plant under a variety of aspects, cal- 

 culated to give general and extended views of the subject, and at the 

 same time impress the mind with a few important distinctions. 



Tournefort dwells chiefly on different aspects and circumstances 

 of the corolla ; — Linnaeus, of the stamens and pistils ; — Jussieu, of 

 the cotyledons and insertion of the stamens. 



Of the comparative merits of these methods, we would observe, 

 that Tournefort's cannot be relied on, because the forms of corollas 

 are often indefinite, and vary into each other ; that of Jussieu ap 

 pears too abstract to be used independently of the aid of some more 

 simple method: — the number of cotyledons, though a definite and im- 

 portant character, cannot, in many cases, be determined without the 

 slow process of waiting for the seeds to germinate ; — the insertion of 

 stamens and of the corolla often appears doubtful, even to the expe- 

 rienced botanist. Much as this method has been admired, it is but 

 little used ; while, on the contrary, that of Linnaeus has, for more than 

 half a century, been regarded as the key to botanical knowledge. 



The characters used in his system are very apparent; and as it 

 refers to the number of parts, rather than to their forms or insertion, 

 it offers to the mind something positive, which is not found either in 

 the method of Tournefort, or that of Jussieu. Between a corolla bell- 

 form, or funnel- form, there are many intermediate forms, which may 

 be as much like one as the other. The insertion over the germ, or 

 mider the germ, are distinct, but the insertion around tlic germ 

 sometimes blends with one, sometimes with the other mode. But 

 between one or two stamens, or one or two pistils, there is no inter- 

 mediate step, or gradual blending of distinctions, which leaves the 

 student in doubt whether the case before him belongs to the one, or 

 the other. 



LECTURE XXIL 



CHARACTERS USED IN CLASSIFICATION. 



LiNN^us, in his " Philosophy of Botany," established three kinds 

 of characters to be used in the description of plants. 



1st. Factitious (or made.) That which is, by agreement, taken 

 as a mark of distinction ; thus, certain circumstances with respect 

 to stamens and pistils are fixed upon for distinguishing classes and 

 orders. Although nature has formed these organs, the arrangement 

 of plants by their means is an invention of man, or artificial. 



2d. Essential Character. That which forms a peculiar character 

 of one genus, and distinguishes it from all other genera. 



3d. Natural Character. This is difficult to define, though it is 

 that which is understood by all; it is the general aspect and appear- 

 ance of the plant, which enables all persons to make a kind of ar- 

 rangement of plants in their own minds, although they would find it 



What is the use of considering different modes of classification'?— What is said of 

 the coniparative merits of the three methods which are mentioned'?— System 9f Lin- 

 naeus offers sometlilng positive— Three kinds of characters to be used in descriptions 

 of plants— Factitious character— Essential character— Natural. 



