PLAKT BREEDING 311 



portant results that have been attained by plant breeders 

 by means of the process of continued selection outlined in 

 Sect. 390. In a general way it may be said that almost 

 any characteristic of a plant or of one of its organs may 

 be made to vary, often in any desired direction. Flowers 

 or fruits may be caused to increase in size many times 

 over; early or late blooming or fruiting may be secured; 

 greater resistance to frost, drought, insects, or parasitic 

 fungi may be developed ; a larger per cent of starch, sugar, 

 or oil in given parts of the plant may be obtained at 

 will. Some instances of such modifications are given in 

 succeeding sections of this chapter, but works on farm- 

 ing and horticulture contain thousands of examples of 

 the sort. 



392. Sugar-Beet Breeding. — Although we are more 

 familiar in this country with sugar made from the sugar- 

 cane, the larger part of the world's supply is manufactured 

 from sugar-beets. Beets of many varieties have been cul- 

 tivated since the sixteenth century or earlier. But it was 

 only as late as the middle of the nineteenth century that 

 scientific efforts were made by Louis Vilmorin to increase 

 the percentage of sugar in beets grown for sugar-making. 

 The sweetest roots are usually the heaviest in proportion 

 to their bulk,^ and therefore Vilmorin tested whole beets 

 or pieces cut from them bj' placing them in brine strong 

 enough to float all of the roots except those which con- 

 tained an unusually large per cent of sugar. These selected 

 beets were planted for seed and became the parents of valu- 

 able new races. 



At present the process of producing beets of the high- 

 est value for the manufacture of sugar is a long and 



1 That is, have the highest specific gravity. 



