XXXIV 
OUTLINES OF BOTANY. 
Species. These tables should be so constructed as to contain, under each bracket, or 
equally indented, two (rarely three or more) alternatives as nearly as possible contradic- 
tory or incompatible with each other, each alternative referring to another bracket, or 
having under it another pair of alternatives further indented. The student having a 
plant to determine, will first, take the general table of Natural Orders, and examining 
his plant at each step to see which alternative agrees with it, will be led on to the 
Order to which it belongs ; he will then compare it with the detaded character of the 
Order given in the text. If it agrees, he will follow the same course with the table of 
the genera of that Order, and again with the table of species of the genus. But in 
each case, if he finds that his plant does not agree with the detailed description of the 
genus or species to which he has thus been referred, he must revert to the beginning 
and carefully go through every step of the investigation before he can be satisfied. A 
fresh examination of his specimen, or of others of the same plant, a critical considera- 
tion of the meaning of every expression in the characters given, may lead him to detect 
some minute point overlooked or mistaken, and put him into the right way. Species 
vary within limits which it is often very difficult to express in words, and it proves 
often impossible, in framing these analytical tables, so to divide the genera and species, 
that those which come under one alternative should absolutely exclude the others. 
In such doubtful cases both alternatives must be tiled before the student can come to 
the conclusion that his plant is not contained in the Flora, or that it is erroneously 
described. 
216. In those Floras where analytical tables are not given, the student is usually 
guided to the most important or prominent characters of each genus or species, either 
by a general summary prefixed to the genera of an Order or to the species of the 
genus, for all such genera or species ; or by a special summary immediately preceding 
the detaded description of each genus or species. In the latter case this summary is 
called a diagnosis. Or sometimes the important characters are only indicated by 
italicizing them in the detailed description. 
217. It may also happen that the specimen gathered may present some occasional 
or accidental anomalies peculiar to that single one, or to a very few individuals, which 
may prevent the species from being at once recognized by its technical characters. It 
may be useful here to point out a few of these anomalies which the botanist may be 
most likely to meet with. For this purpose we may divide them into two classes, viz. : 
1. Aberrations from the ordinary type or appearance of a species for which some 
general cause may be assigned. 
A bright, light, and open situation, particularly at considerable elevations above the 
sea, or at high latitudes, without too much wet or drought, tends to increase the size and 
heighten the colour of flowers, in proportion to the stature and foliage of the plant. 
Shade, on the contrary, especially if accompanied by richness of soil and sufficient 
moisture, tends to increase the foliage and draw up the stem, but to diminish the num- 
ber, size, and colour of the flowers. 
A hot climate and dry situation tend to increase the hairs, prickle3, and other pro- 
ductions of the epidermis, to shorten and stiffen the branches, rendering thorny plants 
yet more spinous. Moisture in a rich soil has a contrary effect. 
The neighbourhood of the sea, or a saline soil or atmosphere, imparts a tlucker and 
more succulent consistence to the foliage and almost every part of the plant, and ap- 
pears not unfrequently to enable plants usually annual to live through the winter. 
Flowers in a maritime variety are often much fewer, but not smaller. 
The luxuriance of plants growing in a rich soil, and the dwarf stunted character of 
those crowded in poor soils, are too well known to need particularizing. It is also an 
everyday observation how gradually the specimens of a species become dwarf and 
stunted as we advance into the cold damp regions of the summits of high mountain- 
ranges, or into high northern latitudes ; and yet it is frequently from the want of at- 
tention to these circumstances that numbers of false species have been added to our 
Enumerations and Floras. Luxuriance entails not only increase of size to the whole 
plant, or of particular parts, but increase of number in branches, in leaves, or leaflets 
of a compound leaf ; or it may diminish the hairiness of the plant, induce thorns to 
grow out into branches, etc. 
