DESCRIPTIVE FLORAS FOR CALIFORNIA, 1838-1880 7 



with a genius for observing plants in the wild, put field work in the forefront of 

 his activities. Had the publication been finished it would have been extremely 

 useful as embodying field studies and was greatly needed, but after leaving Cali- 

 fornia the author's concept of species changed so markedly in the direction of 

 numerous segregation that the completion of the work was not practicable. 



The present Flora of California was planned in 1894. That the work upon it 

 should be done here in California was accepted as a matter of course. While con- 

 venience of access to the older herbaria is lacking, that lack may be compensated 

 for in some measure by journeys to the eastern United States and to Europe. The 

 advantages otherwise are wholly determinative : the living plant associations, their 

 extent, nature and character, — unique and highly informative — stir deeply the 

 scientific imagination. At once a fundamental canon lies plainly in view, that 

 field investigations be given priority, that field work be regarded as primary. In 

 such an ordering of activity all phases of field records and results, all considerations 

 of analysis, all judgments and conclusions of whatever importance at whatever 

 stage derived, whether in the wild, in cultures, in the laboratory or in the her- 

 barium, tie back ultimately as a basic essential to the living plant, and even more 

 expressively, the living plant at a definite locality in a natural plant formation. 



The most significant unit in the classification of living things is, to be sure, the 

 species. It is most important biologically. In any flora the determination of the 

 species and the working concept of the species as a practical matter are all im- 

 portant, since without a sound basis for this biological unit all other considerations 

 fail. On this account it was determined as a matter of fundamental principle 

 that the study of the species should begin (though not end) in the field. 



The field work was designed to favor certain objectives which can be expressed 

 as follows : 



1. Appraisement of natural specific units in the field as a preliminary to cultural or herba- 

 rium determination is to be regarded as a fundamental in scientific method. For a descriptive 

 flora of a region, which is intended to represent plants as they grow in a state of nature, the 

 concept of specific units is best derived in the first instance from the study of genera composed 

 of well-defined units, or from genera which contain highly variable groups in which there is fairly 

 general agreement as to the units. 



2. Appraisement of natural units is definitely furthered by a knowledge of the habitat of 

 the plant, the kind of soil, the amount of moisture, the direction of exposure, and the degree of 



, insolation. 



3. The study of a colony of a species is necessary in order that a series of specimens taken 

 from it may be selected with reference to a plan and therefore serve well as records. Otherwise, 

 there may be accumulations of apparently diverse material which in reality represent only one 

 unit. In small colonies, evidently representing one close genetic assemblage, the essential like- 

 nesses are usually though not always dominant, the variables as a whole inconspicuous or at least 

 so subordinate as to assume a proper relation to the whole social unit. Contrariwise, the prepara- 

 tion of a long series of specimens from either a wide or narrow territory, or from definite pheno- 

 topes, if done with the same care, may result in uncovering two or more units formerly thought 

 to be one. Diagnoses made from living plants or from notes of field studies have, therefore, a 

 vitality and force that are quite lacking in descriptions based only on dried plants. 



4. Investigation of life histories in the field furnishes marked aid in the recognition of 

 specific units. Such factual matter often provides unexpected differentiae of value and affords 

 means for refined discriminations not otherwise possible. In this vast field progress is necessarily 

 slow but the results are always gratifying. The association of various phases of the plant's life 

 with successive ecological factors often supplements morphological character or may provide a 

 basis for species differentiation when morphological characters may be obscure or fail entirely as 

 constant differentiae. Any developmental character may be of interest, or the character of any 

 organ not usually associated with conventional diagnoses. Seedlings or juvenile stages, for ex- 

 ample, often have an importance in determining relationships, because their organs may reveal 

 primitive characters. 



5. Investigation of underground organs, their habit and structure, may yield new facts of 

 importance in connection with relationships. This is all the truer in that such organs are not 

 readily observed and are, save by a few ecologists, rather generally neglected. 



6. Habitat, temperature and precipitation afford a means of determining the natural posi- 

 tion of a species over its entire geographic range, or, in large degree, its climatic requirements, and 



