224 POPULAR SCIENCE MONTHLY 



tribute 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 condi- 

 tions 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 environ- 

 mental 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 jDhenomena 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 ap- 

 praisements of taxonomy. The briefest review of recent literature 

 will reveal the widest diversity of opinion between botanists and zoolo- 

 gists, 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 Oenothera 

 biennis, and 0. grandiflora among the species tested, in addition to 

 furnishing ample exemplification of the derivatives of 0. Lamarckiana, 

 ;*s described by de Vries. Mutations in other genera await further 



