Januaet 15, 1909] 



SCIENCE 



93 



the dominance of the old doctrine of the 

 fixity and inviolability of characters, espe- 

 cially the characters of species. When one 

 holds this view it is very easy for him to 

 find in every variation the indication of a 

 new species, for all one must do is to find 

 that every varietal character is really spe- 

 cific according to such rules as those laid 

 down above by Agassiz. One may logically 

 hold that if characters of a particular kind 

 are of "specific" value, they must be valid, 

 however faiat or obscure they may be. 

 Probably the recently observed activity in 

 the making of new species is the flickering 

 of the dying flame of this expiring theory. 

 Wholly inconsistent with the doctrine of 

 evolution, it must soon die out, and we may 

 well be patient while it lasts, praying in 

 the meantime that its final happy extinc- 

 tion may not be long delayed. 



I need scarcely refer here to the "map 

 theory" of relationship which was once 

 quite the vogue, and of which remnants 

 are still to be seen in some charts showing 

 the relationships of groups. In some of 

 these we still see an attempt to indicate the 

 genetic relationship of a particular group 

 in more than two directions! Before the 

 general acceptance of the doctrine of evolu- 

 tion such an indication of relationship was 

 quite consistent, for into taxonomy no defi- 

 nite conception of genetic relationship had 

 yet entered. Groups of plants were 

 thought of as related to one another, as 

 we think of the relationship of one state 

 to another on a map. And no doubt it was 

 a helpful device for giving clearer notions 

 of the similarities between plant groups. 

 Just as the children in the schools learned 

 much by the exercise of "bounding" the 

 states, so it was profitable in those ante- 

 evolutionary days to use these imaginary 

 maps to show similarities by nearness or 

 juxtaposition. Yet while the practise may 

 once have been profitable, it is no longer 



so, and to engraft genetic ideas upon it is 

 really quite impossible. 



There is still another conception of plant 

 taxonomy to which I must advert, namely, 

 the philosophical division of the vegetable 

 kingdom into convenient groups of various 

 grades, as divisions, subdivisions, classes, 

 subclasses, orders, suborders, etc. Such 

 groups are in a sense natural, in that they 

 are usually characterized by structures 

 which are conceived to have been evolved 

 from others somewhat like them. Yet these 

 have failed to commend themselves perma- 

 nently, no doubt because generally they 

 have been based upon only one or at best 

 a few closely related characters. Thus the 

 somewhat recent attempt to divide the vege- 

 table kingdom into Protophytes and Meta- 

 phytes is an apt illustration, as is also its 

 earlier division into Phanerogams and 

 Cryptogams. And of like nature was the 

 suggestion to divide the dicotyledonous 

 plants into Chalazogamae and Porogamae. 

 The proposal made by Sachs to divide the 

 Thallophytes into Zygosporeae, Oosporeae 

 and Carposporeae, while no doubt it did 

 much to dispel the confusion with regard 

 to the plants included, failed to commend 

 itself generally because it separated clearly 

 related groups of plants. The failure of 

 this arrangement was due not so much to 

 the fact that it was based upon one char- 

 acter—namely, the mode of sexual repro- 

 duction—as to the far more important fact 

 that it took practically no account of the 

 evolution of the plants constituting the 

 groups. Herein was its weakness, and in 

 spite of the advantage of clearness and ease 

 of understanding which it possessed to a 

 marked degree, it was never adopted by 

 systematic botanists. 



A few columns back I said that a natural 

 classification must be an expression of a 

 theory of evolution. I wiU go farther now 

 and say that it is sound scientific practise 



