620 THE SMALL GRAINS 



determined by experiments that rice kernels increase in 

 specific gravity with the degree of ripening. The use of 

 clean seed not only increases the yield, but is one good 

 method of controlling weeds. 



690. Selection. Few or no results have yet been 

 secured from experimental rice selection in this country, 

 though a large number of selections are under trial 

 at the federal and state rice experiment stations. Earli- 

 ness is a quality generally needed. It is urgent in Cali- 

 fornia, to enable the. rice to escape the autumnal rains, 

 and to flower and ripen at the proper time with reference 

 to the occurrence of maximum temperatures. In the 

 Texas-Louisiana rice district, about the greatest need is 

 a variety resistant to the diseases rice blast and straight- 

 head. 



In Japan, a number of selections have been made and 

 exhibited at the Panama-Pacific Exposition, and such 

 work is undertaken in the central provinces of India. 

 Ostiglione is a selection developed in Italy, from the 

 Carolina rice, introduced into that country. 



The importance of mass selection is fust as great in 

 rice-growing as in growing other cereals. The seed plat 

 should, therefore, find a place on every rice farm (see 

 191). 



691. Hybridization. No valuable rice hybrids have 

 yet been established in this country, but a considerable 

 number are under trial by the United States Department 

 of Agriculture. In some cases the effort is being made 

 to fix new varieties that will resist the rice blast and 

 straight-head. Other new varieties are being developed 

 that have combined both the qualities of yield and adapt- 

 ability for milling. A number of apparently valuable 

 hybrids have been created in Japan. 



