SYSTEMATIC IMPROVEMENT OF PLANTS 199 
of inherently superior powers. This cxperiment is so easily 
repeated that it is recommended for the student, and further 
data are hardly necessary in the text (see table, p. 204). 
This method is akin to that employed for the increase of sugar 
in the sugar beet. \When the Germans commenced the improve- 
ment of this crop, the sugar content was low, running from 4 to 
6 per cent, while now whole fields run 15 per cent and occasional 
single beets are found as high as 25 per cent. This improve- 
ment has been effected in the following way. 
Many promising beets are analyzed for sugar content and 
only the highest are selected for planting. The same process 
is repeated for two or three generations, the best individuals 
always being selected as “ mother beets.” The seed from the 
last selection is ‘ multiplied’ in the open field by planting with- 
out selection, simply to secure commercial quantities. Thus 
the commercial seed, while not zimcdiately descended from 
selected beets, is but one or two generations removed from a 
highly selected parentage. 
Crossing to produce new varieties. By the methods above 
mentioned any strain or variety may be greatly improved, but 
by the method of crossing we may bring together absolutely new 
combinations of characters and thereby produce new varieties, 
some of which are certain to be more useful than the old. 
The reasons which practically rule out crossing as a means 
of improvement in animals, except in rarest cases, do not apply 
with much force to plants, because we can produce them in such 
enormous numbers and they are relatively so cheap that we can 
afford to throw away the most of them for the sake of getting 
the few or even the one that is useful. 
Application of Mendel’s law in crossing. The confusing ele- 
ment in crossing is the behavior of dominant and _ recessive 
characters when suddenly brought together in new combinations. 
Reference to the chapter on Mendel’s law will refresh the point 
that characters combine in definite proportions, but that some 
are much more apparent than others which are easily obscured, 
