386 HISTORY OF SCIENCE. 



is particularly displayed. To each species Linnaeus attached a trivial 

 . name, in some cases indicating the place where the plant or animal is 

 found, or its shape, colour, or other remarkable peculiarity; and in 

 other cases where the species has been already commonly distinguished 

 by some well-known name, he retains that name. Thus we have Viola 

 pahtstris (the marsh violet) ; Viola odorata (the sweet violet) ; Viola 

 tricolor (the heartsease or pansy) : Sciurusjavensis (the Javan squirrel) ; 

 Sciurus macrotis * (the long-eared squirrel) ; Sciurus niger (the black 

 squirrel). Again, Tetrao (grouse) is the name of one of the genera in- 

 cluded under the Order of Gallinae (poultry), and the partridge and 

 quail, which belong to this genus, are named respectively Tetrao perdix 

 and Tetrao coturnix. These examples illustrate the improvement in 

 scientific nomenclature that was effected by Linnaeus, when he made 

 the name of each species of animal, plant, or mineral to consist of two 

 words, the first indicating the genus to*which the species, expressed by 

 the second word, belongs. 



The grasp which a well-arranged system of classification gives of 

 objects existing in numbers so vast that no human mind could study 

 them without some co-ordination, will be obvious when we con- 

 sider that though there are now nearly a hundred thousand known 

 species of plants, these are so classified that any given plant can be 

 readily referred to the species to which it belongs. Without some 

 scheme of division and subdivision, it would have been impossible 

 even to find names for each of these hundred thousand species. The 

 binomial system of Linnaeus enables us to give the name of any 

 species with ease and readiness. The system of classification which he 

 applied to plants was, as already observed, an artificial one. It sur- 

 passed all preceding systems in the simplicity of the characters upon 

 which the distinctions were founded; its larger subdivisions were easily 

 retained in the memory; and though it separated in many cases nearly 

 allied species, this imperfection was obviated by some modifications 

 in the rigidity of its application. Again, some of the characters are 

 not invariable ; and another defect is that unless a plant were given 

 in full flower, it is impossible to determine from it the Class and Order 

 to which it belongs. Its author was himself sensible of these imper- 

 fections, and at the same time that he elaborated his system as the 

 most useful index to the place of a given plant in the vegetable world, 

 he declared that a natural system was the great desideratum of classifi- 

 catory botany. Linnaeus divided the vegetable kingdom into Classes, 

 the Classes into Orders, the Orders into genera, and genera into species. 

 The characters of the Classes are founded on the number, situation, 

 relative lengths or arrangement of the stamens, which usually admit of 

 easy observation. The Classes are twenty-four in number, and they are 

 thus named : 



* A word of Greek derivation, signifying long-eared. 



