llV OUTLINES OF BOTANY. 



perseverance, 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 in the right way. Even experienced botanists, pro- 

 vided with the most detailed descriptions 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 ex- 

 clude all that come under the other one. In such cases it has been found 

 expedient to make both alternatives lead to the doubtful genus or species, 

 although for brevity's sake this has been avoided when not thought abso- 

 lutely 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 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 

 italicising 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 re- 

 cognised by its technical characters. It may be useful here to point out 

 a few of these anomalies which the botanist will 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 eleva- 

 tions 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 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 par- 

 ticularising. It is also an everyday observation how gradually the speci- 

 mens 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 circum- 

 stances that numbers of false species have been added to our Enumerations 



