NATURAL HISTORY OF THE EIGHTEENTH CENT. 385 



thirdly, each Order into genera. The next step he makes is to divide 

 each genus into species. The name assigned by Linnaeus to each species 

 is expressive of the essential difference between that and every other 

 species belonging to the same genus. His definitions or descriptions 

 of the species include generally, in a very few words, some distinc- 

 tion which completely identifies the animal in question, whereas a long 

 and laboured description was previously required. The importance of 

 definite plans of arrangement, in the study of the almost infinite di- 

 versity of objects which nature presents, will be obvious to every person 

 who has ever had occasion to deal with a series of objects of even 

 limited number and diversities. For example, every one who has a few 

 scores of books on his shelves is obliged to arrange them in some 

 fashion or other. The basis of the arrangement may be the sizes, or 

 the bindings, or the dates, or the^subject matter, according to the con- 

 venience of the person who is to use them. Similarly a man of busi- 

 ness may arrange his letters according to the names of his correspon- 

 dents, or those of the places from which they are sent, or by the dates 

 or the subjects to which they relate. Each arrangement, having for its 

 object nothing but facility of reference in the examples just adduced, 

 may bring together books or letters which have no other connection 

 with each other ; and the same thing will be true also, to a greater or 

 less extent, of classifications of natural objects which regard facility of 

 reference. Thus, reversing some of the plans of classification which 

 writers on botany had recourse to before the time of Linnaeus, we find 

 some authors adopting an alphabetic arrangement; others classing plants 

 according to their time of flowering; others, according to ftut places in 

 which they grow; others, according to their medicinal properties. But 

 Nature, though following no arrangement or system, has established 

 certai ; similarities about numbers of "her productions that cannot be 

 overlooked. Thus, in the vegetable world there are general resemblances 

 of appearance, habit, flowers, fruit, etc., amongst extensive series of dif- 

 ferent kinds of plants. An arrangement founded upon such groups of 

 character, duly co-ordinated, would give what is termed the natural 

 method, in which objects originally allied would appear in due relation 

 with their neighbours. Botanists, however, for a long time drew up 

 systems founded rather on distinctions of someone part of a pi ant, which 

 would give a ready plan of reference. Gesner, Csesalpinis, Morison, 

 Ray, Rivini, Boerhaave, Tournefort, selected either the fruit, or the 

 flower, or both. Magnal published in 1720 a scheme in which the 

 forms of the calyx (the cup-shaped circle of leaves which usually sup- 

 port the gayer coloured petals of the corolla) are used as the basis of 

 the arrangement. Linnaeus was the first who made the stamens and 

 the pistils the bases of an artificial system of classifying plants, and he 

 was induced to select these organs on account of their importance and 

 the readiness with which they could be observed. In the concise de- 

 scriptions he gives of these specific differences the genius of Linnaeus 



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