256 GENETICS [BoT. Absts., Vol. VII, 



1774. Jelinek. Nachste Aufgaben der Pflanzenziichtung und der Sortenpriifung. [The 

 nextproblemsof plant-breeding and variety testing.] Zeitschr. Pflanzenziicht. 7: 83-90. Dec, 

 1919. — It has been shown that a variety (of wheat) selected as pure line may show great varia- 

 tions in yield in different years and it has been proposed to mix selected pure lines to secure 

 varieties better than either single pure line or original "Landsorten." Increased yield due to 

 individual reaction of variety or its components to various vegetative factors. This capacity 

 to react differs among various lines of a variety and is hereditary. Relation of inherent reac- 

 tion to vegetative factors may be shown graphically by Stempel type of "correlation curve." 

 Limiting values which indicate range of correlation curve and which form limiting condi- 

 tions of existence for variety are called "vegetation limits" of variety or line. The "renting 

 capacity" of variety is conditioned by limiting minimum and maximum values of vegeta- 

 tion factors, defined by harvest value and its production costs. "Renting capacity" is neces- 

 sarily not constant. Lines with narrow vegetation limits have also narrow renting capacities 

 but lines with broad vegetation limits may have narrow or broad renting capacity according 

 to whether the correlation curve rises and falls quickly or gradually at either end. Limits 

 between which vegetative factors of locality vary relatively to soil and varying weather con- 

 dition in any year are termed "vegetation limits of the locality." Varieties with narrow 

 correlation curve react very easily to changes of growth conditions and may be designated as 

 irritable varieties; and conversely, plastic varieties exist. In selecting varieties for any 

 locality care should be taken that varietal renting capacity is not narrower than vegetation 

 limits of given region. Sufficient plasticity of any variety is important in agricultural prac- 

 tise, especially where growth conditions vary widely. Pure lines are necessarily non-plastic. 

 If highest type variety is to consist of selected mixture ("individually selected population") 

 of pure lines, then parent variety must be preserved in original condition. Certain difficul- 

 ties would attend formation of proper mixture of lines but these should not be considered 

 insuperable. — L. R. Waldron. 



1775. Johnson, Charles W. Variation of the palm weevil. Jour. Heredity 11 : 84. 1 fig. 

 1920. — -Palm weevils {Rhynchophorus cruentus Fabr.) were collected showing practically con- 

 tinuous color intergradations.— J. H. Beaumont. 



1776. Johnson, James. An improved strain of Wisconsin tobacco. Connecticut Havana 

 No. 38. Jour. Heredity 10:281-288. Fig. 8-10. June, 1919.— Seed from about thirty-five 

 self-fertilized plants of Connecticut Havana tobacco were sown in progeny rows and it became 

 evident that three types were represented in the progeny. Two types differed from the 

 normal and were constant in later generations. They are undoubtedly mutations. A cross 

 between these gave an intermediate which in two years and among large numbers did not 

 segregate, though exact data were not taken. Seed was distributed and in 1919 it has displaced 

 other strains of tobacco. [See also Bot. Absts. 7, Entry 1694.] — J. H. Beaumont. 



1777. Jones, D. F. The effect of inbreeding and crossbreeding upon development. Proc. 

 Nation. Acad. Sci. 4: 246-250. 2 fig. Aug., 1918. — Continuing inbreeding experiments of 

 East and Hayes, author finds no further reduction in vigor after eight inbred generations. 

 Two inbred lines, though less productive than original parents, are still quite fertile; others 

 have run towards either pollen or ovule abortion. Crossing different inbred lines enormously 

 increases vigor, frequently bringing gain in yield of 180 per cent. Mixtures of own and foreign 

 pollen, applied to silks of both parents, result in selective fertilization favoring own pollen. — ■ 

 Merle C. Coulter. 



1778. Jones, D. F. Heritable characters of maize. IV. A lethal factor — 'defective seeds. 

 Jour. Heredity 11: 161-167. 7 fig. April, 1920. — A factor, development of pericarp but 

 incomplete development or complete suppression of embryo and endosperm, is to be distin- 

 guished from partially developed ovules due to incompleted growth or ineffective fertilization. 

 If genetically defective seeds appear on a self-fertilized plant they will be in approximately 

 the ratio 3:1. Several other factors may be operating, however, so that much more work 

 must be done to check up the inheritance of this factor.— J. H. Beaumont. 



