SELECTION IN PLANT BREEDING 193 
for they knew that many times they had noticed and isolated plants 
showing new characters from their cultures, and had carefully made 
selections for further improvement of the new strain, but that genera- 
tion after generation showed no further progress. LeCouteur, whom de 
Vries cites as the first known user of the pedigree culture method, had 
a case in point. From the heterogeneous lot of wheat plants which he 
was growing, he isolated a uniform type of great merit which he called 
“ Bellevue de Talavera.” For years after, this strain was subjected to 
selection in order to bring about further improvement, but the efforts 
were made in vain, for no new heritable variations were produced. Yet 
something was lacking from this theory. Sometimes there did appear 
to be a gradual improvement by selection. De Vries said that this was 
merely a temporary improvement made by selection of quantitative 
variations. He believed that when selection ceased, sooner or later 
the improved types would return to the original type of the variety 
from which it had been produced. The real interpretation of the facts 
and one which fitted all the parts of the puzzle together, came from the 
work of Johannsen and later investigators. It is an explanation that 
should have been thought of before, but like many other important dis- 
coveries, it was too simple for ordinary minds to grasp. Weismann had 
shown years before that the inheritance of characters acquired through 
outside influences during the development of the body was probably 
mythical. His investigations led him to believe that there is a continu- 
ity between the reproductive or germ cells of different generations, and 
that the body is nothing but a temporary house built to shelter them. 
Injuries to the house have no effect on the future generations unless the 
germ cells themselves are affected. Later Boveri and others, through 
their cytological studies, showed that the future germ cells are laid down 
at a very early stage in certain animal organisms and that very few cell 
divisions take place before the maturation of the reproductive organs 
and the production of active germ cells. The body cells he found to be 
built up by continuous cell division of a very different part of the orig- 
inal fertilized egg. Since no biologist, however, had found or is likely to 
find similar cytological phenomena in plants, no one seemed to grasp 
the idea that here was the key to the question that had been puzzling 
the plant breeders. Johannsen, however, brought matters straight by 
his experiments on beans. He found that commercial varieties of 
beans, though pure in grosser characters, such as color, were actually 
very mixed types when such characters as length or weight were studied. 
Several investigations were undertaken on size characters, the char- 
acters most rapidly affected by changes in environment. He found that 
his commercial variety fluctuated around an average size and that when 
seeds iarger or smaller than this type were selected they responded to 
it in whichever direction the selection was made. The progeny of the 
