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f 1. 8
h. hl. h 2. h 3. h 4. h 5.
i. il. i 2. i 3.
i 4. 1. 11.
Scales or glands, whether hypogynous or epigynous.
(Nectarium of Linnæus.)
crease the fruit in size, or surmount it, or are adherent
the simple caryopsis of Grasses.
m 1. m 2.
n 1. n 2. n 3. n 4. n 5. n 6. n 7.
n 8. n 9.
o 3. 04. o 5.
pl. P 2.
Plumula. p 3. Radicle.
two following, s 1. and 2. s 1. A compound flower.
The locusta of a Grass (either one-flowered or many
flowered.) t. The involucrum of an umbel, or a head. tl. The involucrum of a compound flower. (Calyx com
munis of Linnæus.) t 2.
Glume of Grasses. (Calyx of Linnæus.) t 3. Outer calyx of Malvaceæ, Dipsaceæ, Brunoniaceæ. t 4. Involucrum of Ferns. (Indusium of Swartz.) t 5. Bracteæ. t 6. Scales of a catkin. t 7. • Paleæ. t 8. The paraphyses of Mosses. t 9. The calyptra when formed of connate bracteæ.
Receptacle of a single flower. ul.
Common receptacle either of a compound flower, a
catkin, or a head. Placed under one of the above (thus .*), shows that a
part is expanded, or opened, by force. + Indicates a vertical section (used thus, t+4).
Indicates a transverse section (used thus, ::).
PHYTOGRAPHY; OR, OF THE RULES TO BË OBSERVED
IN DESCRIBING AND NAMING PLANTS.
I now proceed to investigate the principles upon which plants are described and named. It would be impossible for any person to recognise a plant which had been discovered by another, unless such a description of it were put upon record as should express all its essential features; and unless it were, at the same time, furnished with a distinctive name, it could never be subsequently spoken of intelligibly. For these reasons, the mode of describing and naming plants is one of the most important practical subjects in the science.
It may appear, at first sight, extremely easy to describe a plant, and we constantly find travellers and others attempting to do so in vulgar language; but their accounts are usually so vague, that no distinct idea can be formed of the subject of their descriptions, which remains an enigma until some botanist, following their steps, shall happen to be able to put its characters into scientific language.
The great object of descriptions in Natural History is, to enable any person to recognise a known species, after its station has been discovered in a classification; and also to put those who have not had the opportunity of examining a plant themselves into possession of all the facts necessary to acquire a just notion of its structure and affinities.
There are two means of effecting this object; the one by means of detailed descriptions, the other by the aid of briefer abstracts of the most essential characters only.
OF DIAGNOSES; OR, OF GENERIC AND SPECIFIC CHARACTERS.
We have seen that plants are distinguished from each other by their characters: of the application of these characters we must now speak. Were each species to be characterised independently of other species, and to be described with all the minute circumstances of structure that belong to it, the progress of investigation would be too slow, and the length of time requisite to acquire information much too great: for this reason, the process of enquiry has been simplified, by collecting in groups all those species which have certain great characters in common, and abstracting those characters, which then become the distinctions of classes: the species of a class are again collected into other groups, agreeing in some other common peculiarities, which are in like manner abstracted, and form the characters of orders. Thus reduced in extent, the species of each order are submitted to the same process of combination; the characters by which they are combined become distinctive of genera; and the species are, finally, left shorn of the greatest part of their characters, which are thus reduced within a very narrow compass. Each plant has, therefore, four characters; or, if sub-classes, sub-orders, or other modes of division are adopted, as many separate characters as there may be divisions,
These characters are of two sorts; the one called essential, the other differential. The former are the most commonly employed for orders and genera; the latter are chiefly used in discriminating species: the former are the most valuable, and will probably, in time, supersede the others, which convey little information, and are only useful in aiding us in our analysis of large bodies of species: the latter are often called definitions; but, as no definite limits can be traced between living things, a strict definition in Natural History becomes impracticable, for which reason the term differential must be admitted instead.
Differential characters express, in the least possible space, the distinctions between plants: they should contain nothing superfluous, nor any thing which can be considered implied by the contrasted characters of those with which they are to be compared. By this means the distinctions of species are brought into the least possible compass; and the analysis of their characters becomes so effectual, that a botanist is expected to be able, without difficulty, to determine the exact station and name of any one of the 100,000 species supposed to exist. Nothing can sound better than this; but, unfortunately, the advantages of differential characters are not quite so great as would appear. In sacrificing every thing to brevity, it is found in practice that doubts and ambiguities are continually created; and for this especial reason, among others, that differential characters must necessarily be framed upon a consideration of what we know, and not with reference to what we do not know: on this account, a differential character, constructed in the most unexceptionable manner by one botanist, may be unintelligible to another who possesses more knowledge, or a greater number of species. For example, when Linnæus framed the differential character of Rosa indica, “germinibus ovatis pedunculisque glabris, caule subinermi, petiolis aculeatis,” it probably distinguished that species from all others that he knew: but our acquaintance with Roses is so much more extensive than that of Linnæus, that we have many Roses to which his character is equally applicable. A differential character, moreover, conveys no information beyond that of the differences between one thing and another, and can be viewed in no other light than as a convenient method of analysis. For this reason, the essential character is more generally adopted at the present day, either to the exclusion of the differential character, or in union with it.
The essential character of a plant expresses, as its name implies, those peculiarities which are known by experience to be most essential to it; but admits nothing unimportant or