Page:Popular Science Monthly Volume 69.djvu/228

224 to the progress of exact knowledge of genetics, or methods and manner of inheritance.

The combined and organized efforts of all the botanists in the world concentrated upon all the herbaria in existence would add but little to existing conclusions upon this subject, if we may judge by past achievements or immediate promise, while the most precise information upon geographical distribution can be of interest only in deciphering what has been accomplished, what forms exist and where, the factors influencing their movements, and where these have probably originated.

To appreciate the mechanism of heredity an exact knowledge of the nature and behavior of the bodies which form its physical basis must be gained. To ascertain the action of heredity, statistical and accurate observations must be made upon long series of pedigreed progenies, and these must be carried out in such manner that environmental conditions may be either controlled or their influence measured. Pedigree-culture, first extensively applied by de Vries to clovers, teasels, poppies, snap-dragon and evening-primroses with such marked success, and notf used by many workers with animals as well as plants, has proved to be one of the most efficient forms of research yet used by the biologist, and its usefulness is hardly beginning to be realized. The various phases of selection, the accurate measurement of fluctuating variability, correlations, the amount and character of the influence of environmental factors, the effects of close and cross breeding, and the detection of saltatory variations may be accomplished under circumstances which allow a thorough and exact appraisement of the general physiological value of such phenomena by the use of cultures in continuous series.

While the phases of evolution are generally estimated in terms of origin or formation of species, the basal problems of heredity are not especially concerned with the taxonomic estimation given by this author or that author as to the taxonomic standing of any form, nor does it matter whether it is a subspecies, elementary species or 'real' species. The questions of evolution are to be answered by the acquisition of more accurate knowledge concerning the accession, modification or loss of functions, capacities and characters of physiologically unified groups of organisms, regardless of the necessarily more or less artificial appraisements of taxonomy. The briefest review of recent literature will reveal the widest diversity of opinion between botanists and zoologists, and also unexplainable differences among botanists and zoologists as to the species-conception. The value of discussions into which such possible differences may enter is not enhanced by this fact.

The carrying out of pedigree-cultures in New York has revealed the occurrence of discontinuous variants or mutants in Œnothera biennis, and O. grandiflora among the species tested, in addition to furnishing ample exemplification of the derivatives of O. Lamarckiana, as described by de Vries. Mutations in other genera await further