182 



consider it a species, although exhibiting no difference of aspect, pro- 

 vided it can be defined, even although the differences are so minute 

 that they can be detected only by the microscope ; while a third party 

 are of opinion that the validity of a species may be tested by cultiva- 

 tion. The Authors are not inclined to believe that any one of these 

 tests is sufficient. Of all the works of Creation, we have a specific 

 account only of Man ; but as the others appear to be formed on the 

 same plan, there is a strong presumption in favour of those arguments 

 which assimilate the species of plants to what we know of the human 

 race. With regard to mankind, it is universally acknowledged that 

 there now exists so great diversity between an inhabitant of the torrid 

 and an inhabitant of the frigid zone, and even of any one part of the 

 globe and of another, that it can only be accounted for on the princi- 

 ple that each succeeding generation has a tendency to recede more 

 and more, in general appearance, from the original type ; and if we 

 apply this to the Vegetable Kingdom, we must at once allow that, 

 although cultivation may sometimes in a single year or two satisfacto- 

 rily show that two supposed species are the same, a thousand years' 

 cultivation caimot prove them distinct. The more we cultivate a 

 plant, or the more it is limited in its wild state to a particular climate 

 or place of growth, the more permanency is given to the peculiarities 

 of what was originally derived from the same root, or even seed-vessel, 

 of another apparently widely different form. Hence a rare moun- 

 tainous plant may frequently be a mere alpine permanent state of 

 some common lowland species, or a Swedish species the more north- 

 ern race or state of a southern one ; and it is from this cause that we 

 see in our gardens so many called species (as in the genus Achillea), 

 which cannot now be referred satisfactorily to any of the wild ones, 

 although primarily derived from them. Knowing, then, this tendency 

 of Nature to give permanency to a variety of forms obtained from one 

 primitive species, there appears to be less violence done to her laws 

 by combining too much, than by subdivision, unless where there is an 

 anatomical or physiological distinction. Linnseus took nearly all his 

 specific characters from conspicuous parts, especially from the stem 

 and foliage, and they were therefore natural ; but at the present day 

 we are prone to select minute ones : of these some are of trifling value, 

 while others, sufficient to constitue subgenera, are connected with the 

 habit of the plant, and should therefore not be neglected. Indeed the 

 time may ere long arrive, when what are now called genera or sub- 

 genera will alone be considered species, and another Linnaeus be 

 requisite to reduce the chaos into order. In the meanwhile, we have 



