Apeil 8, 1921] 



SCIENCE 



345 



eties. He advocates as an aid to specialized corn 

 breeding the formati-on of a Corn Becord Associa- 

 tion for the registration of promising selfed 

 strains. By proper encouragement, he believes 

 that retired farmers could be interested in the de- 

 velopment of selfed strains of corn as a hobby. 



Progress report on the method of selection in 

 self-fertilized lines: D. F. Jones. Selection in 

 self-fertilized lines makes possible a control of 

 the heredity from both the pollen parent and seed 

 parent. Some seventy-five lines selected in this 

 way and started from four different varieties 

 chosen from among the best as grown in Connecti- 

 cut have shown the usual segregation of type and 

 reduction in vigor. Many clear-cut undesirable 

 characters have appeared and are being eliminated. 

 For example: fifteen lines have contained various 

 forms of chlorophyll-deficient seedlings; ten, the 

 "defective seed" factor; three, different forma of 

 dwarf plants; two, golden plants; three, varie- 

 gated plants; and five, various forms of sterility. 

 Along with these outstanding weaknesses other 

 marked variations in height, size of stalk, type of 

 tassel and ear, and color of foliage have appeared. 

 Such differences as these form the material for 

 effective selection for productiveness. 



Overcoming "root rot" by treeding: W. D. 

 Valleau. In breeding for resistance to corn root 

 rot, the fact should be kept in mind that disease- 

 free seed probably does not exist, under average 

 field conditions. All plants examined in the field 

 as well as those grown in the sand box have been 

 found to be infected. Differences in time of death 

 of plants of a given variety under field conditions 

 are dependent on differences in resistance of the 

 plants to root rot, and are not the result of plant- 

 ing diseased or disease-free seed. Various seed 

 treatments, including all of those commonly recom- 

 mended for small grains, have faUed as a means 

 of control. Attempts to obtain disease-free seed by 

 harvesting before ripening and protecting ears from 

 further infection has failed as infection occurs be- 

 fore the milk stage. Ears may be graded accord- 

 ing to resistance by growing seedlings in a sand 

 box and noting the time required for the individ- 

 ual seedlings to rot to the surface of the sand. By 

 this method premature death of plants has been 

 reduced from an average of 36.1 in the checks to 

 8.4 per cent, in the plants from the most resistant 

 ears. An attempt is being made to obtain pure 

 lines of the most resistant strains by self-pollina- 

 tion. Self-pollination, even for many years, does 

 not materially reduce the number of days between 



the death of the first and last plant from a given 

 ear, over open-pollinated ears, in the sand box. 

 Preliminary experiments indicate that field selec- 

 tion of seed from the longest-lived plants may 

 prove a means of obtaining seed of a high degree 

 of resistance. 



Ear type selection and yield in corn: T. A. 

 KiESSELBACH. From the seed standpoint, ear 

 characteristics of dent corn fall into two classes, 

 utilitarian and non-utilitarian. The utilitarian 

 characters comprise those which indicate sound- 

 ness and hereditary adaptation to certain environ- 

 mental conditions. This adaptation can not be 

 reliably forecasted by a, mere ear examination. 

 However, associated with marked differences in 

 the plant growth habits resultant from corre- 

 sponding regional differences in the environment 

 (and especially climatic differences), are found 

 rather distinct adaptive ear type characteristics. 

 The more adverse plant growth conditions are for 

 corn, the more nearly do the adapted types ap- 

 proach the small stalk, low leaf area, slender ear 

 ajid smooth shallow kernel of flint corn. Approach 

 of a balance or equilibrium between adverse en- 

 vironment and the plant and its ear type, is fre- 

 quently spoken of as "running out" of the corn, 

 whereas such a reaction is an actual betterment for 

 the prevailing conditions. The corn grower is 

 coming to recognize the advantage of modifying 

 his conception of ear type to harmonize with the 

 environment of his locality. There is no such 

 thing as a universal best type, 



Progress report on corn disease investigations: 

 James R. Holbeet. Cooperative investigations by 

 the Bureau of Plant Industry and certain agricul- 

 tural experiment stations during the past three 

 years have shown that the root, stalk and ear rot 

 diseases of corn are widely distributed in this 

 country wherever corn is grown. These diseases 

 have been found to be a limiting factor in corn 

 production. They may be largely controlled by 

 careful field selection of healthy, productive 

 plants, physical selection of seed ears, and the 

 proper use of the germination test, as described in 

 Farmer's Bulletin 1176. The continued selection 

 of seed according to these recommendations has 

 been effective in improving a number of varieties 

 of corn. Other means for control, such as the 

 breeding of resistant varieties, soil sanitation, and 

 the use of certain soil correctives, are being in- 



The present status of continuous selection ex- 

 penments with corn: L. H. Smith. Several lines 



