AUTHORS' PREFACE 



XV 



having a distinct centre (although this may not always be repre- 

 sented by a typical form), around which is a field of variation 

 almost unlimited in extent, and yet having certain, though still 

 undetermined, boundaries. 



The idea of the species, in short, rests upon the fact that all the 

 individuals of which it is composed are, to an indefinite extent, 

 capable of being fertilised by one another, and only by one another. 

 Now, as long as it has not been proved that a variety artificially 

 produced by man has ceased to be capable of being fertilised 

 when crossed with other individuals of the same species, while 

 it continues fertile to an indefinite extent when impregnated 

 by individuals of its own special form, — so long it cannot be said 

 that a new species has been brought into existence ; and, up to 

 the present, no one, so far as we are aware, has ever asserted that 

 such a case has occurred. Far from it, indeed, as this capability 

 of being fertilised by its own members, and only by them, consti- 

 tutes, so to say, the very essence of the species. It is this which 

 alike ensures its permanence, its pliability, and its power of adapting 

 itself to the various conditions under which it may be compelled to 

 exist. 



Reverting, however, to the plan of our work, we have taken care 

 not to give any names that are not really in common use and well 

 known, and have avoided mere translations. In publishing syno- 

 nyms, we have been very cautious, taking especial care not to admit 

 any that are not thoroughly well established, and, in most cases, 

 verifying them by a comparative cultivation of those plants which 

 we considered identical. Having accurately identified each plant 

 under consideration by giving its botanical and various common 

 names, we mention its native country, adding a brief history of the 

 plant, when we possess any reliable data on this subject. After 

 mentioning the native country and giving the history of the plant, 

 we describe its mode of growth, whether annual, biennial, or 

 perennial. Here it should be remarked that many plants are grown 

 in the kitchen garden as annuals which are biennial or perennial 

 as regards their fructification. For kitchen-garden purposes, it is 

 enough that these plants attain in their first year a size sufficiently 

 large for table use, and this is especially the case with most plants 

 which are grown for their roots, such as Carrots, Beet-roots, Turnips, 

 Radishes, etc. 



The descriptions, properly so named, of the different kinds of 



