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XXXIV 



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OUTLINES OP 



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dent having a plant to determine, will first take the general table of Natural Orders, 

 and examining his plant at each step to see M'hich alternative agrees with it, will be 

 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 

 inust 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 ]>ut him into the right way. Species vary within ^mits 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 

 18 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 

 giiided 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 

 precedmg the detaded description of each genus or species. In the latter case this 

 summary is calle<l a diaonosis. Or sometimes the important characters are only 

 indicated by italicizing them in the detailed description, , v 



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

 accidental anomalies peculiar to that single one, or to a very few individuals, 



"Which may prevent the species from being at once recognised 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, 

 into two classes, viz. : 



{I.) Abtrrationsfrom the ordinary type or appearance of a species for which some 

 general cause may be assigned. 



A bright, lidit, and open situation, particularly at considerable elevations above 

 the sea, or at hidi 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 suffi- 

 cient moisture, tends to mcrease the foliage and draw up the stem, but to dimi- 

 nish the number, size, and colour of the flowers. 



A hot climate anddrj^ situation tend to increase the hairs, prickles, and other 

 productions of the epidermis, to shorten and stiffen the branches, renderincr thorny 

 plants yet more spinous. Moisture in a rich soil has a contrary effect. ° 



Ihe neighbourhood of the sea, or a saline soil or atmosphere, imparts a thicker 

 and more succulent consistence to the foliarre and almost every part of the plant, 

 and api>car3 not unfrequentlj- to enable plants usually annual to live through the 

 winter Flowers in a maritime variety are often much fewer, but not smaller. 



Ihe 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 e yer>'day 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-rangos, or mto high northern latitudes ; and yet it is frequently from the want 

 of attention to these cn-cumstances 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. 



Ur^T ""^^^ '"'^''^^'i'^^"^ ^^wing, lie close upon the ground, wiU often become 

 J^^A f^ succulent, and less readdy dehiscent, than those which are not so ex- 

 posed to the moisture of the sod. ; 



For this purpose we may divide them 



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