GENERAL PRINCIPLES OF CLASSIFICATION. 387 



seed ; so that we may from analogy infer that they have all 

 issued originally from one common stock. Thus if we walk 

 into a field of Wheat, Barley, or Oats, we observe thousands of 

 individuals, which, although differing to a certain extent in size, 

 and in some other unimportant characters, we at once associate 

 together under a common name. In like manner we commonly 

 observe around us, in the gardens and fields, similar collections 

 of individuals. Such collections of plants, thus seen to resemble 

 each other in all their important parts, constitute our first idea of 

 a species ; and that idea is at once confirmed if, by taking the 

 seeds of such plants and sowing them, we obtain other plants 

 resembling those from which such seeds have been derived. 



Varieties. — It has just been observed, that if the seed of a 

 species be sown it will produce a plant resembling its parent 

 in all its important parts. This will, however, only happen, 

 when the new individual has been exposed to similar influences 

 of soil, heat, light, moisture, &c., as its parent ; and hence we 

 find that any variations in such particulars will lead to certain 

 peculiarities in form, colour, size, and other minor characters, in 

 plants raised from the seeds of the same species. In this manner 

 we have produced what are termed varieties. In some cases such 

 variations are merely transient, and the individuals presenting 

 such peculiarities will in time return to their original specific 

 type, or perish altogether; while in other instances they are 

 permanent and continue throughout the life of the individual, 

 the whole plant being, as it were, impregnated with the parti- 

 cular variations thus impressed upon it, and hence such variations 

 may be perpetuated by the gardener in the operations of Bud- 

 ding, G-raftiug, &c. (see page 96), as is the case with many 

 of our fruit trees and flowers. Even these varieties, however, 

 cannot be propagated by seed, for if their seeds be sown, the 

 individuals which will be produced will have a tendency to re- 

 vert to the original species from Avhich such varieties have been 

 obtained, so that the nature of the plant raised will depend chiefly 

 upon that of the soil in which it is placed. Thus, if we sow the 

 seeds of a number of different kinds of Apples, the fruit which 

 will be afterwards produced by the new generation of Apple trees, 

 will, instead of resembling that of their parents, have a tendency 

 to revert to that of the Common Crab, from which species all 

 such variations have been originally derived. Hence a variety 

 differs from a species in the fact that it cannot be propagated by 

 seed. 



Races. — Besides the varieties just alluded to there are others, 

 which are c?i\\%(\. permanent varieties or races, because their pecu- 

 liarities can be transmitted by seed. Familiar examples of such 

 races are afforded by our Cereal grains, as Wheat, Oats, Barley, 

 &c., and also by our culinary vegetables, as Peas, Lettuce, Ra- 

 dishes, Cabbages, Cauliflower, and Broccoli. How such races of 

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