XXXIV 
OUTLINES OF 
dent 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 he 
led on to the Order to which it belongs, he will then compare it with the detailed 
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 investiga- 
tion before he can be satisfied. A fresh examination of his specimen, or of others 
of the same plant, a critical consideration 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 analy- 
tical 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 alter- 
natives must be tried before the student can come to the conclusion that his plant 
is not contained in the Flora, or that it is erroneously described. 
246. 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 detailed 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. 
247. 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 proportiou to the stature and foliage 
of the plant. 
Shade, on the contrary, especially if accompanied by richness of soil and suffi- 
cient moisture, tends to increase the foliage and draw up the stem, but to dimi- 
nish the number, size and colour of the flowers. 
A hot climate and dry situation tend to increase the hairs, prickles, and other 
productions 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 thicker 
and more succulent consistence to the foliage and almost every part of the plant, 
and appears 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 moun- 
tain-ranges, or into high northern latitudes ; and yet it is frequently from the want 
of attention 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. 
Capsules which, while growing, lie close upon the ground, will often become 
larger, more succulent, and less readily dehiscent, than those which are not so ex- 
posed to the moisture of the soil. 
