Makch 10, 1916] 



SCIENCE 



339 



another uncertainty. Supposing that the 

 second of two investigators whose results 

 are to be compared, has based his work on 

 correctly identified material, can it be as- 

 sumed that the first investigator has taken 

 equal pains to identify his material? Un- 

 fortunately this assumption may be with- 

 out sufficient foundation. One must con- 

 sider the probability of error. The paper 

 recording results may show internal evi- 

 dence of a satisfactory nature. The author 

 may state the origin of his material or note 

 the care taken in its identification, or that 

 it was submitted to a specialist. Any such 

 internal evidence increases confidence in 

 the results. If the plants used by both in- 

 vestigators of this hypothetical pair have 

 been accurately identified we may apply 

 the mathematical axiom, things equal to 

 the same thing are equal to each other. 

 However, the probability of error is very 

 greatly reduced if direct comparison can 

 be made. This can be done only if each in- 

 vestigator has preserved the plants he has 

 studied. This leads me to make this plea 

 to botanists. Let every worker preserve 

 the specimen he has studied if his results 

 are in any way connected with the identity 

 of the species. I think that anatomists, 

 cytologists, morphologists, and others that 

 study the internal structure of plants, are 

 in the habit of preserving in alcohol or 

 other liquid, the portion of the plant with 

 which they have worked. Specimens of 

 this kind should always be preserved in 

 order that observations may be confirmed, 

 but fragments, such as these are likely to 

 be, are not usually sufficient for taxonomic 

 identification. For the latter purpose a 

 specimen should be prepared and placed in 

 a public herbarium, accompanied by a 

 label bearing the data necessary to connect 

 the specimen with the investigation that it 

 supports. If such supporting evidence is 

 at hand any controversy as to the identity 



of the plants studied by different workers 

 can be settled by consulting these herbarium 

 specimens. The physiologist may find it to 

 his advantage to follow the same proced- 

 ure. His work is often with plant life in 

 general rather than with particular species. 

 But whenever his investigations concern 

 definite species he should preserve her- 

 barium specimens. The ecologists are fond 

 of giving lists of plants growing under 

 certain conditions and comparing these 

 plants with those growing under similar 

 conditions elsewhere. In the early days 

 of this younger branch of botanical sci- 

 ence little attention was paid to the identity 

 of the species, and still less to preserving 

 representative specimens. The subject was 

 lightly waved aside with the assertion that 

 they were not concerned with the identity 

 of the individual species, only with the as- 

 pect of the vegetation. The modern school 

 of ecologists, I am pleased to say, takes a 

 more serious view of the role played by 

 definite species. If it is worth while pub- 

 lishing a list of species at all, it is worth 

 while supporting the record with perma- 

 nent evidence. The geneticists, a young 

 and active brood of investigators, will find 

 it to their advantage also to adopt the 

 method outlined above. The living speci- 

 mens are the best of evidence while they 

 exist, but at best they are evanescent. Her- 

 barium specimens, if properly prepared 

 and properly cared for afterwards, are 

 permanent. If his plants have been passed 

 upon by a general taxonomist or better by 

 a group specialist the non-taxonomist may 

 be deluded with the idea that his record is 

 complete, that the identity of his species is 

 beyond question and is fixed for ever and 

 ever. Such an assumption depends upon 

 the infallibility of taxonomists. I can as- 

 sure you, however, that taxonomists are 

 very fallible. Specialists may not agree 

 among themselves on the identity of a 



