This is safe and to a certain degree judicious, no doubt, as respects published species.  Once admitted, they may stand until they are put down by evidence, direct or circumstantial.  Doubtless a species may rightfully be condemned on good circumstantial evidence.  But what course does De Candolle pursue in the case—­of every-day occurrence to most working botanists, having to elaborate collections from countries not so well explored as Europe—­when the forms in question, or one of the two, are as yet unnamed?  Does he introduce as a new species every form which he cannot connect by ocular proof with a near relative, from which it differs only in particulars which he sees are inconstant in better known species of the same group?  We suppose not.  But, if he does, little improvement for the future upon the state of things revealed in the following quotation can be expected: 

“In the actual state of our knowledge, after having seen nearly all the original specimens, and in some species as many as two hundred representatives from different localities, I estimate that, out of the three hundred species of Cupuliferae which will be enumerated in the Prodromus, two-thirds at least are provisional species.  In general, when we consider what a multitude of species were described from a single specimen, or from the forms of a single locality, of a single country, or are badly described, it is difficult to believe that above one-third of the actual species in botanical works will remain unchanged.”

Such being the results of the want of adequate knowledge, how is it likely to be when our knowledge is largely increased?  The judgment of so practised a botanist as De Candolle is important in this regard, and it accords with that of other botanists of equal experience.

“They are mistaken,” he pointedly asserts, “who repeat that the greater part of our species are clearly limited, and that the doubtful species are in a feeble minority.  This seemed to be true, so long as a genus was imperfectly known, and its species were founded upon few specimens, that is to say, were provisional.  Just as we come to know them better, intermediate forms flow in, and doubts as to specific limits augment.”

De Candolle insists, indeed, in this connection, that the higher the rank of the groups the more definite their limitation, or, in other terms, the fewer the ambiguous or doubtful forms, that genera are more strictly limited than species tribes than genera, orders than tribes, etc.  We are not convinced of this Often where it has appeared to be so, advancing discovery has brought intermediate forms to light, perplexing to the systematist.  “They are mistaken, we think more than one systematic botanist will say, “who repeat that the greater part of our natural orders and tribes are absolutely limited,” however we may agree that we will limit them.  Provisional genera we suppose are proportionally hardly less common than provisional species; and hundreds of genera are