OtlTLiNES OF BOtANt. xxvii 



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 investigation 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 di£fioult 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 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 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 speeies for which some general cause 

 may he 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 fiowers, 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 number, size, and colour 

 of the flowers. 



A hot cUmate and dry situation tends 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 unfre- 

 quently 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 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 exposed to the moisture of 

 the soil. 



Herbs eaten down by sheep or cattle, or crushed underfoot, or otherwise checked in their 

 growth, or trees or shrubs out down to the ground, if then exposed to favourable circumstances 

 of soil and climate, will send up luxuriant side-shoots, often so different in the form of their 

 leaves, in their ramification and inflorescence, as to be scarcely recognizable for the same species. 



Annuals which have germinated in spring, and flowered without check, will often be very 

 different in aspect from individuals of the same speeies, which, having germinated later, are 

 stopped by summer droughts or the approach of winter, and only flower the following season 

 upon a second growth. The latter have often been mistaken for perennials. 



Hybrids, or crosses between two distinct species, come under the same category of anomalous 

 specimens from a known cause. Frequent as they are in gardens, where they are artificially 

 produced, they are probably rare in nature, although on this subject there is much diversity o£ 

 opinion, some believing them to be very frequent, others almost denying their existence. 

 Absolute proof of the origin of a plant found wild, is of course impossible ; but it is pretty 

 generally agreed that the following particulars must always co-exist in a viild hybrid. It 

 partakes of the characters of its two parents ; it is to be found isolated, or almost isolated, in 

 places where the two parents are abundant ; if there are two or three, they will generally be 

 dissimilar from each other, one partaking more of one parent, another of the other ; it seldom 

 ripens good seed ; it will never.be found where one of the parents grows alone. 



