Maech 10, 1916] 



SCIENCE 



335 



only as an example of how such work 

 suffers by being far removed from the field 

 of experimental research. 



The taxonomist arrives at results not by 

 the application of the experimental method, 

 but by the repetition of observations. To 

 be sure the geneticists are applying the ex- 

 perimental method with considerable suc- 

 cess, but their results can have no immediate 

 bearing on the subject under discussion. 

 Ascertaining facts by the method of re- 

 peated observations lacks the precision and 

 definiteness of the experimental method. 

 The examination of hundreds of herbarium 

 specimens, plant mummies, is not so fasci- 

 nating nor so satisfying as it is to set up a 

 piece of apparatus and see something hap- 

 pen. I believe this is the chief reason why 

 so many of our keenest minds have hesi- 

 tated to join the ranks of the descriptive 

 taxonomists, the results appearing to them 

 indefinite in proportion to the time and 

 energy spent in obtaining them. 



Now let me review with you the scope of 

 taxonomy in the broad sense, the science of 

 classification. To me the two great ques- 

 tions that botanists seek to answer are, how 

 do plants live? and how are plants related? 

 Most botanical investigations can be used 

 as an aid in answering one or the other of 

 these questions. From this standpoint the 

 two fundamental divisions of botany are 

 physiology and taxonomy. Many facts in 

 physiology may be established by experi- 

 ment. Most facts in taxonomy are estab- 

 lished by repeated observation. Various 

 subsidiary branches of botany may aid one 

 or the other of these fundamental divisions 

 according as the facts obtained are used in 

 answering the main question. Morpholog- 

 ical studies gather certain facts which in 

 themselves are interesting, but which reach 

 their highest usefulness only when struc- 

 tural morphology yields to physiology and 



comparative morphology yields to tax- 

 onomy. 



Taxonomy in the general sense is the sci- 

 ence of classification. But the taxonomy 

 with which we are concerned is that which 

 attempts to answer the question, how are 

 plants related. The very question implies 

 that plants are related. Our taxonomy as- 

 sumes the evolutionary hypothesis that all 

 the organisms of the present day have de- 

 veloped or evolved from other somewhat 

 different organisms of the past. The great 

 truth which taxonomy is seeking to express 

 is the genetic relation of organisms. If the 

 genetic history of all organisms were known 

 the classification of these organisms would 

 be merely an arrangement of facts. But 

 the genetic history of organisms is not 

 known, or known only for an infinitesimal 

 number for an infinitesimaUy short period 

 of time. Our classification of plants is, 

 then, an expression of judgment as to what 

 are the probable genetic relations of these 

 organisms. At the best this classification 

 can represent only a cross section of the 

 lines of phylogenetic development. It may 

 be compared to a formula in calculus with 

 a large number of variables. The value of 

 the formula may be found for any given 

 moment by substituting the values that the 

 individual variables have at that same 

 moment. 



Some workers in this broad field of syste- 

 matic botany are studying the relations of 

 the more comprehensive subdivisions of 

 plants such as the families, orders and 

 groups higher than these. In such investi- 

 gations they seek for resemblances, as it is 

 these upon which, rather than upon differ- 

 ences, the interpretations of relationship 

 must be based. Some botanists, on the other 

 hand, are concerned chiefly with the deter- 

 mination of the relations of the ultimate 

 systematic groups of organisms, the species 

 and their subdivisions. Here the observer 



