OUTLINES OF BOTANY. xlix 



After a little habit, this mechanical process will be much abridged. The 

 great divisions of the general analytical table will be at once recognized, and 

 very soon the large Orders and genera will become so familiar, that in most 

 cases the amateurs will only have to commence with them. Yet in all cases 

 of doubt and hesitation, wherever the plant does not agree perfectly with the 

 generic character and description, he must revert to the beginning, and carefully 

 go through every step of the investigation before he can be satisfied. 



And notwithstanding the care that has been bestowed on the framing of the 

 analytical keys of the present work, and the number of cases in which they have 

 been verified, specimen in hand, through every stage, it cannot be hoped that 

 they have been rendered so precise as to preclude doubt. The beginner es- 

 pecially will often be at a loss as to which alternative agrees the best with the 

 plant he is examining, and one false step may lead him faraway from the object 

 he is seeking. But let him not be discouraged ; perseverance, a fresh examina- 

 tion 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 in the right 

 way. Even experienced botanists, provided with the most detailed descrip- 

 tions in systematic works of the highest repute, are occasionally led into false 

 determinations. Species vary within limits which it is often very difficult to 

 express in words. In making an analytical table, it often proves impossible so 

 to divide the genera or species which have to come under one bracket, as that 

 each alternative must exclude all that come under the other one. In such 

 cases it has been found expedient to make both alternatives lead to the doubt- 

 ful genus or species, although for brevity's sake this has been avoided when not 

 thought absolutely necessary. 



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 sum- 

 mary 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 de- 

 scription. 



247. It may also happen that the specimen gathered may present some oc- 

 casional 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 anoma- 

 lies 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 sta- 

 ture 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 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 



d 



