154 DE VRIES— ELEMENTARY SPECIES IN AGRICULTURE. [April i8 



years his pedigree must have gained a degree of uniformity, which 

 is in no need of any further improvement. The real act of effect- 

 ive selection is thereby brought back to the first years, but how many 

 generations of true selection it has taken to render the rye of Schlan- 

 stedt uniform and pure it will, of course, always remain impossible 

 to tell. The explanation of Rimpau's success must, therefore, for a 

 large part remain hypothetical. If now we try to give such an ex- 

 plication on the ground of the theory of mutation and of the already 

 quoted discoveries of Nilsson we may suggest the following : At the 

 period when Rimpau started his pedigree, his rye fields must have 

 contained numerous elementary species, not observed or distin- 

 guished by him or by any other agriculturist of his time. Among 

 the ears which he selected a good number of these aberrant types 

 will, of course, have been represented, since he selected only those 

 which caught his eye by some striking useful difference from the 

 main type. Of course, he sought for ears of one and the same ideal 

 type, having a large number of big kernels. But notwithstanding 

 this, his handful of ears must have belonged to more than one ele- 

 mentary species. Among these units of his selection some will have 

 been better yielders than others, and the subsequent selection of his 

 twenty years of pedigree-culture will slowly but surely have elim- 

 inated the units of minor worth. This would result, at the end, in 

 a complete isolation of the best one of all the types, which he orig- 

 inally, but unconsciously, selected and mixed. 



Or, in other words, Rimpau's pedigree culture was started as a 

 mixture of a number of excellent types, and his yearly selection 

 gradually reduced this number, until he had isolated and purified the 

 very best one among them. This point was, of course, only uncon- 

 sciously reached, but then it must have made his rye independent of 

 all further real selection, reducing the process to the care of ex- 

 cluding vicinism. 



If this explication of Rimpau's process is true it, of course, holds 

 good for all similar cases of slow and gradual amelioration of agri- 

 cultural plants by selection. Thereby it would deprive the theory of 

 the origin of species by small and continuous changes of its last sup- 

 port in the realm of the vegetable kingdom. 



