432 



SCIENCE. 



[N. S. Vol. VIII. No. 196. 



on Rhamnus Frangula, with perhaps two 

 other forms to be separated from the old P. 

 coronata. Puccinia rubigo-vera is separated 

 into three species, P. glumarum, P. dispersa 

 and P. simplex— the distinctions based 

 largely on the presence or absence of the 

 ^ecidium, although there are also certain 

 differences in the habit and color of the 

 other stages. The three original species are 

 split up into seven species, besides two un- 

 certain forms, characterized in the main by 

 physiological characters. Furthermore, of 

 P. graminis, six specialized forms are enu- 

 merated, characterized by differences in the 

 inoculating capacity of the uredo or teleu- 

 tospores on different hosts. The other 

 species also have their specialized forms, 

 the total number being, I believe, twenty- 

 eight. We may consider the specialized 

 forms to be races, and in that case, cer- 

 tainly, we shall have to agree with Eriks- 

 son and Henning in considering their seven 

 species as species rather than races. The 

 important point is to know whether the 

 differences observed are temporary and ac- 

 cidental or permanent. It is too much to 

 ask for the confirmation of the results of 

 these two experimenters just now, for their 

 work is recent and has been carried so far 

 beyond that of previous experimenters that 

 it must require a considerable number of 

 years before we could expect the work to be 

 repeated by others. So far as the experi- 

 ments have been repeated, as in the case of 

 P. coronifera and P. coronata, it has been 

 confirmed. 



Enough has been said to show that the 

 conception of species by those who are 

 ■doing the most advanced work in fungi is 

 much more flexible than it used to be, and 

 significance is to be attached to the fact 

 that the number of those who, as viewed by 

 the typical systematic botanist, hold very 

 heterodox views is increasing. The ex- 

 planation is to be sought in the fact that 

 descriptive botany in certain groups of 



plants has reached a point where the ordi- 

 nary morphological characters no longer 

 suffice to classify what we know or wish to 

 know about the plants themselves. It was 

 my privilege eleven years ago to address 

 what was then the Biological Section of the 

 Association on a subject somewhat related 

 to that of to-daj^, and my closing sentence 

 then was : " Following the prevailing 

 tendency in business affairs, the question 

 they [botanists] ask of plants is not so 

 much, ' Who is your father and where did 

 you come from,' as ' What can you do? ' " 



The tendency noticed eleven years ago is 

 even more marked at the present day. As 

 compared with the times of which I at- 

 tempted to give a sketch in my opening re- 

 marks, I think we may truly say that 

 whatever may be the case in zoology, in bot- 

 any theoretical considerations with regard 

 to evolution play a much less important 

 part than they used to. In the case of such 

 plants as Lycopodiacese, EquisetacetB and 

 their allies and of certain orders of phan- 

 erogams the ancestral question naturally 

 remains as important as ever, but, although 

 papers. on other orders of plants accom- 

 panied by hypothetical genealogies and 

 family trees of the banyan type appear at 

 not infrequent intervals in botanical jour- 

 nals, they are quite overshadowed in gen- 

 eral interest by the papers on cytology, life- 

 histories and physiology. That was not 

 the ease in the sixties, when nothing com- 

 pared in interest with the question of the 

 origin of species. While we cannot be too 

 grateful to Darwin for having opened our 

 eyes to see the value of evolution in gen- 

 eral, the majority of the active botanists of 

 the present day find too many other pres- 

 sing questions to be solved to be able to 

 dwell on evolution to the same exclusive 

 extent as did the botanists of the last gen- 

 eration. 



Our definition of a species included two 

 terms which required further explanation. 



