130 CHARACTERS USED IN CLASSIFICATION. || 
in their structure, exogenous in their mode of growth, and their leaves l| 
are distinguished by branching;, reticulate veins. 
Comparison of the Methods of Tournefort, lAnnceus^ and Jussieu. 
We have now piesented the pupil with the outhnes of three modes \i 
of classification, exhibiting the plant under a variety of aspects, cal- m 
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 j — 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 nitmber 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 LinucEus has, for more than j 
half a century, been regarded as the key to botanical knowledge. j 
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 
under the germ, are distinct, but the insertion around the 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. 
4 
LECTURE XXIL 
CHARACTERS USED IN CLASSIFICATION. 
LiNNJEus, 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 pecuhar 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 7 — What is said of 
ilie comparative merits of the three methods which are mentioned'? — System of Lin- 
naeus oners someliiini^ positive— Three kinds of characters to be used in descriptions 
ol plants — Faoliuous character — Essential character — Natural. 
