4 THE PHYLOGENETIC METHOD IN TAXONOMY. 



between the families concerned. While interpretation will always play a part in taxonomy, the general use 

 of experiment will leave much less opportunity for the personal equation than is at present the case. Taxonomy, 

 like descriptive botany, is based upon the species, but, while there may exist a passable kind of descriptive 

 botany, there can be no real taxonomy as long as the sole criterion of a species is the difference which any 

 observer thinks he sees between one plant and another. The so-called species of to-day range in value from 

 mere variations to true species which are groups of great constancy and definiteness. The reasons for this 

 are obvious when one recalls that 'species' are still the product of the herbarium, not of the field, and that 

 the more intensive the study, the greater the output in 'species.' It would seem that careful field study of 

 a form for several seasons would be the first requisite for the making of a species, but it is a precaution which 

 is entirely ignored in the vast majority of cases. The thought of subjecting forms presumed to be species 

 to conclusive test by experiment has apparently not even occurred to descriptive botanists as yet. Notwith- 

 standing, there can be no serious doubt that the existing practice of re-splitting hairs must come to an end sooner 

 or later. The remedy will come from without through the application of experimental methods in the hands 

 of the ecologist,' and the cataloguing of slight and unrelated differences will yield to an ordered taxonomy." 



Duly. — While the first duty of taxonomy is to furnish the best possible record of 

 evolution and relationship, its next most important task is to be of the greatest usefulness. 

 Fortunately, there is nothing antagonistic between these two needs, for the taxonomy 

 that is based upon phylogeny is not only by far the most useful, but can also be made 

 the most convenient and usable. For all who deal with plants, and even for the system- 

 atist outside his own groups, the most usable taxonomy is that in which relationship 

 reaches its fullest expression, both in the forms recognized and the names applied. 

 This leads to easier recognition of the plant and readier application of its name, a result 

 to which even the specialist can not be indifferent, unless he be of the narrowest type. 

 Even with our present unsatisfactory taxonomy, the number of people that make use of 

 it has steadily increased, owing to the breaking down of the artificial barriers between 

 the sciences and the rapid development of the practical fields of agriculture, grazing, 

 and forestry. The time is past when even a morphologist or cytologist can afford to 

 boast that he does not know a single plant by name, while for the geneticist and ecologist, 

 species and variads" are the very essence of their work. The gradual disappearance of 

 the unnatural boundary between botany and zoology makes it all the more necessary to 

 have a kind of systematic botany that appeals to the zoologist, whose general use of the 

 trinomial indicates a greater feeling for relationship. The use of genera and species 

 by the agronomist, grazing expert, and forester is fundamental, and is limited only by 

 the convenience and intelligence of the taxonomic treatment available. Even with 

 those to whom plants are not the immediate object of attack, such as soil chemists 

 and physicists, topographers, geologists, etc., much more attention would be given 

 vegetation if manuals met their needs. 



SCIENTIFIC BASIS OF TAXONOMY. 



Classification and relationship. — The need of classifying plants has been felt since 

 Aristotle (334 b. c), and the history of classification is one of attempts to achieve a 

 more natural system, except for the artificial system of Linnaeus (1737). The natural 

 classification of flowering plants properly dates from Jussieu (1789), since which time 

 progress has been chiefly crystallized in the systems proposed by DeCandoUe (1813, 

 1819), Endlicher (1836), Lindley (1845), Bentham (1862), Eichler (1876), Luerssen 

 (1882), Engler (1892), and Bessey (1896). In spite of its apparent simpUcity and great 

 popularity, the Linnaean system gradually yielded to the CandoUean and Benthamian 

 during the first half of the nineteenth century. The spirit of development that swept 

 through botany with the rise of the cell-theory and the consequent impetus to physiology 

 and morphology reacted favorably upon taxonomy. During the following half-century, 



* By the term ecologist is understood anyone that employs quantitative and experimental methods in the study of 

 plants or animals in the natural habitat. 



' This term is employed for any form of the species, as discussed on p. 23. 



