424 PRACTICAL BOTANY 



the original ems. Usually the best ear is used for staminate plants and 

 planted on each alternate row in the small breeding plot. All the plants 

 from the other ears going into the plot are detasseled. 



The pedigreed ^ strains produced in the breeding plot are multiplied 

 for general field use and also furnish ears of varying worth for a second 

 ear-row test, if it is desired to continue the improvement. 



The ear-row test need not be isolated, for no seed is taken from it. 

 Neither is there any need for detasseling until the breeding plot is 

 reached. 



388. Sugar beet breeding. Almost all the sugar that is used 

 by civilized peoples is manufactured frora sugar cane and 

 sugar beets, the latter furnishing the greater part of the world's 

 supply. Beets of many varieties have been cultivated since 

 the sixteenth century or earlier. But it v^as 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 

 by placing them in brine strong enough to float all of the 

 roots except those which contained an unusually large per cent 

 of sugar. The sugar beet is ordinarily (though not always) 

 a biennial, and the root produced in one year is used for grow- 

 ing seed in the second year. These selected beets were planted 

 for seed and became the parents of valuable new races. 



At present the process of producing beets of the highest 

 value for the manufacture of sugar is a long and complicated 

 one, consisting, as usually carried out, of the following steps : 



(1) Planting the best seed that can be bought. 

 . (2) Chemically testing average samples of the roots that 

 are grown from the seed of (1) to see if they are good enough 

 to breed from. 



(3) Selecting the best single roots by a chemical test. Less 

 than one half of one per cent of all the beets tested pass this 

 examination in a satisfactory way. 



1 Pedigreed, because the pedigree on both sides is a matter of record. 

 ^ That is, have the highest specific gravity. 



