74 Transactions. 



the latter are known, or believed, to be connected at the present day 

 by intermediate gradations, whereas species were formerly thus connected 

 . . . We shall have to treat species in the same manner as those 

 naturalists treat genera who admit that genera are merely artificial 

 combinations made for convenience." : ' This," concludes Darwin, " may 

 not be a charming prospect, but we shall at least be freed from the vain 

 search and undiscoverable essence of the term ' species.' " 



Notwithstanding the last-quoted words of Darwin, the painstaking and 

 epoch-making researches of Jordan, Mendel, de Vries, Bateson, Johannsen, 

 and others have shed such light upon the species-question that the relation 

 between a species and its subdivisions stands out far more clearly than in 

 Darwin's time. Of especial importance is the fundamental difference shown 

 by de Vries* between unfixed variants, whose forms depend upon the environ- 

 ment, and his elementary species (microspecies) which come true from seed 

 under different outer circumstances — a distinction quite unsuspected by the 

 early naturalists, as seen from the quotations already cited, so far as groups 

 distinguished by quite trivial characters were concerned. In other words, if in 

 the light of modern knowledge not only were the pre-Darwinian definition 

 of Bentham to be accepted, but even that of the post-Darwinian Bomanes, 

 species after species would have to be rejected, variety after variety 

 would be raised to specific rank, though others would be cast aside as mere 

 fluctuations, and hundreds of trivial forms, apparently identical, as gauged 

 by floristic methods, would have to be accepted as valid species, because 

 they fulfilled perfectly the breeding test. Needless to say, the confusion 

 would quickl} r become indescribable. 



Some Considerations prom the Foregoing regarding Species and 



Varieties. 



What, then, should be done in order to make a flora serve its primary 

 purpose of enabling any member of a plant-population to be readily recog- 

 nized ? First of all, most will agree that no drastic changes are advisable. 

 Linnean aggregate species answer admirably, provided it be understood 

 that such are groups of varieties connected, it may be, by intermediate 

 hybrids, and that species of this kind do not exist in nature as true-breeding 

 entities, while their limitations are a matter of individual taste and not of 

 scientific fact. 



What really do occur in nature are the individuals, and these, 

 obviously, should be the starting-point of classification. Unfortunately, 

 these individuals are not all biologically equal. Some reproduce their like, 

 and groups of these are the true self-breeding entities — i.e., the microspecies, 

 or biotypes. Others are of hybrid origin, and should, on the one hand, 

 segregate in Mendelian fashion, or, on the other hand, be more or less inter- 

 mediate in character between the parent species and come true from seed. 

 Others, again, according to those believing either in natural selection or in 

 neo-Lamarckism, should be neither microspecies nor hybrids, and would be 

 expected in course of time to give rise sexually to individuals more or less 

 distinct from their parents. Whether this last class really exists is, in the 

 opinion of some, not scientifically established. It may quite well be that all 

 " intermediates " which are not microspecies are merely hybrids between 

 these latter or between the hybrids themselves. The hybrids of taxonomists 

 are the result of crosses between one variety of a Linnean species and that of 



* Die Mutationstheorie, Bd. 1, Lief. 1, pp. 32-41, Leipzig, 1901. 



