PLANT BREEDING 177 



in this respect, so that it is sometimes necessary to select 

 only about one best beet out of every thousand to grow seed 

 for the next crop. 



In the case of plants grown for the production of seed of 

 standard varieties for the market, as beans, peas, or any of 

 the many flowers (such as sweet peas), in regard to which 

 there is much competition, great attention is paid to weeding 

 out and destroying plants that do not conform to the standard. 

 This process is called roguing. The maintenance of the breed 

 depends largely upon the intelligence and thoroughness with 

 which it is carried out. 



168. Ancient and modern plant breeding. No one knows 

 when plant breeding began, because the earliest attempts of 

 man to cultivate useful plants date back to unknown antiquity, 

 and it is highly probable that the first growers of plants for 

 human food more or less unconsciously selected the best seeds 

 to be sown for a new crop, and were thus really practicing 

 plant breeding. Among the Chinese, agriculture began at 

 least 4600 years ago, and for a considerable part of that time 

 they have paid much attention to the perpetuation of desirable 

 varieties of the plants of the farm and garden. 



Modern plant breeding did not begin at any definite date. 

 Some valuable work was done in selecting and propagating 

 improved varieties of wheat in Great Britain as early as the 

 first quarter of the nineteenth century, but it was not until 

 toward the middle of the century that many investigators 

 began to try to put plant breeding on a scientific foundation, 

 working with plants ranging all the way from the cereals to 

 sugar beets. One of the main problems in plant breeding is 

 that of predicting the way in which the characters of a plant 

 will be inherited by its descendants. In a large number of 

 cases, a number which is rapidly increasing, it is possible to 

 make such predictions with scientific accuracy. These are 

 based on the immense mass of data which has been gained 

 from tens of thousands of experiments made by scientific 

 investigators and by practical plant breeders everywhere. 



