SHULL: DUPLICATION OF A LEAF-LOBE FACTOR 443 
The morphological complexity of the character produced by the 
B and B’ factors is believed to indicate that duplication has come 
about through a physical rearrangement in the genotype rather than 
by a repeated mutation affecting in like manner chromosomes belong- 
ing to distinct pairs. 
My acknowledgments and thanks are due to the following corre- 
spondents, to whom I am indebted for seeds of the wild biotypes which 
were used in the present study: D. T. MacDougal, F. Shreve, 
J. M. Shull, C. A. Shull, A. H. Trow, Tine Tammes, G. Bitter, E. 
Baur, L. Gross, G. Molon, and T. Z. Chang. 
i 
LITERATURE CITED 
Bridges, C. B. Deficiency. Genetics 2: 445-465. 1917. 
Gates, R. R. On Successive Duplicate Mutations. Biol. Bull. 29: 204-220. 1915. 
Hallqvist, Carl Ein neuer Fall von Dimerie bei Brassica Napus. Bot. Not. 1: 
39-42. I916. 
Howard, A., and Howard, Gabrielle L. C. On the Inheritance of Some Characters 
in Wheat I. Mem. Dept. Agr. India 5: No. 1. 1912. 
— On the Inheritance of Some Characters in Wheat II. Mem. Dept. Agr. 
India 7: 273-285. I9I5. 
Ikeno, S. Variegation in Plantago. Genetics 2: 390-416. 1917. 
Morgan, T. H., Sturtevant, A. H., Muller, H. J.,and Bridges, C.B. The Mechanism 
of Mendelian Heredity. Pp. xiii + 262. New York: Henry Holt & Co. 
IQI5. 
Nilsson-Ehle, H. Einige Ergebnisse von Kreuzungen bei Hafer und Weizen. 
Botaniska Notiser, pp. 257-294. 1908. 
— Kreuzungsuntersuchungen an Hafer und Weizen. Lunds Universitets 
Arsskrift, INSEE Atdi2 Bde s-oNr: 2. pp: 122. VlQoo: 
Shull, G. H. Results of Crossing Bursa bursa-pastoris and Bursa Heegeri. Proc. 
7th Internat. Cong. Zoél. 1907, Boston 1912. ‘‘ Advance reprint ”’ in 1910, 
6 pp. 1907. 
— Bursa bursa-pastoris and Bursa Heegeri: Biotypes and Hybrids. Carnegie 
Institution of Washington. Publ. No. 112, pp. 57. 1909. 
— Defective Inheritance-ratios in Bursa hybrids. Verh. d. naturf. Verein 
Briinn 49: 157-168. I9gII. 
—— Duplicate genes for capsule-form in Bursa bursa-pastoris. Zeitschr. f. ind. 
Abstamm.- u. Vererb. 12: 97-149. I914. 
