INTRODUCTION. 



13 



practical scientist will not attempt it. The steady disappearance of recognized and 

 recognizable species removes all their landmarks, and they come to look upon descriptive 

 botany as hopeless. Their unanimously expressed opinions of it would doubtless be 

 salutary, if these could only reach the ears for which they are intended. Meanwhile, 

 the gap between the systematists and those they should serve widens, and it can only 

 be bridged by a type of botany that frankly regards the needs of the latter as paramount. 

 These needs are the very ones that arise out of evolution and relationship. 



The nature of the grievance felt by those who would use taxonomy against the method 

 of segregation may be readily understood by reference to tables 1 and 2. In the Rocky 

 Mountain region the number of species has increased from 1,905 to 5,100 in 30 years, 

 and these are now to be sought among 950 genera in place of 551. The species of 91 

 representative large genera have grown from 962 to 3,576, or almost fourfold. This is 

 reflected in the average number of species per genus, which was 10 in 1885 and 39 in 

 1917. In the largest genera the increase is often greater; for example, Eriogonum has 

 grown from 27 species to 122, Salix from 16 to 76, Phacelia from 6 to 44, Krynitzkia from 

 11 to 68, Potentilla from 16 to 99, Lwpinus from 13 to 80, Aster from 40 to 139, Senecio 

 from 21 to 114, and Poa from 12 to 67. Aconitum with 1 species in 1885 now has 11, 

 Dodecatheon has increased from 1 to 18, Frasera from 1 to 11, Gutierrezia from 1 to 11, 

 and Chrysopsis from 1 to 27. In the case of Pentstemon with an increase from 27 to 98 

 species, a further segregation (Pennell, 1920) has resulted in a total of 125 species, and 

 this can be maintained as long as new personal judgments are brought to the task. This 

 is fully confirmed by the fact that the species of 1909 are regularly intermediate in number 

 between those of 1885 and 1917. This total represents only a 43 per cent increase, 

 however, while the number for 1917 constitutes a further increase of 124 per cent. 



When definite ecological investigation was begun in the Rocky Mountains in 1899, 

 much enthusiasm was felt for the recently segregated units, as it was supposed that the 

 contention that a finer analysis would be helpful to the ecologist was correct. For 6 

 or 8 years an endeavor was made to utilize the increasing crop of segregates in ecological 

 studies, both in vegetation and in experimental evolution. Gradually it became evident 

 that the so-called new species were herbarium-made, and could not be expected to fit 

 the facts in the field, while it was quickly realized that they ignored relationships instead 

 of suggesting them. In short, when they existed outside the herbarium, they made 

 correlation difficult or impossible instead of aiding it. As a consequence of this attempt 

 to make use of segregates, it was realized that the ecologist could work only with more 

 objective units, checked by statistics and experiment, and based to the fullest degree 

 upon evolutionary relationship. The outcome was "Rocky Mountain Flowers" 

 (Clements and Clements, 1913), in which a definite endeavor was made to relate the 

 myriad forms to definite specific stocks. This was done purely from the ecological 

 and evolutionary viewpoints, and without any reference to previous treatments, with 

 the exception that a few generic segregates were retained for practical reasons. In fact, 

 the earlier treatment of Coulter, which followed closely that of Gray, was completely 

 lostltojview, and was not taken into account until the preparation of tables 1 and 2 



Table 1. — Number of genera and species in Rocky Mountain tnanuals. 



> Extraregional units excluded. 



