116 On the requisites necessary 



to the discovery of that natural system upon which the great Author 

 of Nature has planned the works of creation, or as regards the detec- 

 tion of those laws hy which the several functions of vitality are re- 

 gulated. In all probability, there is ample scope for the accumu- 

 lated observations of many generations yet to come, before we can 

 expect that either systematic botany or vegetable physiology will 

 take up their position by the side of the exact sciences. In the pre- 

 sent state of our knowledge, there is perhaps most to be expected, 

 towards making some decided step in advance, from those botanists 

 who have it in their power to attend to the cultivation of plants in 

 all its practical details. So far as any thing can be expected from 

 direct observation on the structure of individual specimens, there are 

 plenty of willing workmen of the most able class both at home and 

 abroad, but there is a decided want of scientific experimenters, and 

 until further information can be obtained from the positive results of 

 experiment, we may scarcely hope to establish on a very firm basis, 

 any of the more important principles of the science. Notwithstand- 

 ing that every classification of plants proceeds upon the predetermi- 

 nation of the specific characters of individuals, hundreds of examples 

 might be produced in proof of the real ignorance of our very first rate 

 botanists, as to the limits within which a species may vary. In some 

 cases they are tolerably agreed about arranging as a single species 

 numerous forms possessing a marked dissimilarity ; and here they 

 have been guided either by the results of experiment, or they have 

 had the opportunity of seeing so many intermediate forms between 

 two of the most marked varieties, as to leave no doubt that all were 

 referable to a common origin. There are, however, a multitude of 

 instances where the resemblance which two individuals, of somewhat 

 different form, in certain respects, is decidedly striking, and which 

 are nevertheless almost universally considered to belong to different 

 species. There is, in short, no law whatever hitherto established, 

 by which the limits of variation to a given species can be satisfac- 

 torily assigned, and until some such law be discovered, we cannot 

 expect precision in the details of systematic botany. In this respect 

 the science is pretty much in the position which mineralogy occupied 

 before the discovery of the laVs of crystallography ; mineralogists 

 were frequently in the dark as to what crystals were to be included 

 under one species, and they knew almost nothing of the numerous 

 forms in which any given species might occur, until they were ac- 

 tually found to exist. But now, a single crystal at once puts the 

 mineralogist in possession of the primitive form of the species, and 

 he can calculate " a priori" the possible forms under which it may 

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