HEREDITY OF COLOR IN PHLOX DRUMMONDII ' 



By Arthur W. Gilbert, 

 Professor of Plant Breeding, New York State College of Agriculture at Cornell 



University 



INTRODUCTION 



Workers in the field of heredity, stimulated by Gregor Mendel's 

 classical experiments, are attempting to prove or disprove the hypothesis, 

 which is now quite generally accepted, that plants and animals are com- 

 posed of distinctly heritable units, now called "unit characters." After 

 the presence of these units has been demonstrated, the next problem is 

 to determine what these units are in different plants and animals, and 

 their exact mode of inheritance. 



These experiments were planned to solve these problems with Phlox 

 drummomlii. 



METHODS OF PROCEDURE 



This plant was chosen because its flowers have a wide range of colors, 

 it is easy to grow both in the greenhouse and out of doors, and crossing 

 is not difficult. 



Commercial seed was purchased and the different varieties grown and 

 self-fertilized for three years, so as to be sure of pure types. The varieties 

 used in these experiments were found to breed true for three years and 

 are assumed to be pure. 



The crossing was done in the ordinary way, great care being exercised 

 at all times to prevent the admission of foreign pollen. All flowers were 

 carefully bagged with small oiled bags, which were tied as tightly 

 around the stem as the growth of the plant would permit. The parents 

 were self-fertilized each year and grown alongside of the Fj and Fj 

 hybrids. 



Not(?s were carefully made of the color of the flowers, according to 

 the nomenclature in Repertoire de Couleurs.^ Inasmuch as the color 

 fades rapidly in intense sunlight, the descriptions were made soon after 

 the flower had first opened. These colors are described in the tables 

 by naming the number of the page and the shade which corresponds 

 nearest to it. 



' Paper No. 53, Department of Plant Breeding, Cornell University, Ithaca, N. Y. 



2 The foIlowinR color book was used as a standard basis of comparison of the colors: Soci^t^ Francaise des 

 Chrysanthtaiistes. Repertoire de Couleurs. 82 p., illus., 3 pi. (2 col.), and 365 col. pi. in 2 portfolios. 

 Paris, 1905. 



Journal of Agricultural Research, Vol. IV, No. 4 



Dept. of AKriculture, Washington, D. C. July 15, 1915 



N. Y. (Cornell)— 1 



(293) 



