84 University of California Publications in Agricultural Sciences [Vol.4 



Apparent mutants were first found in tlie course of worli on 

 anotlier problem, the relation of temperature to variation (Frost, 

 1911), conducted at Cornell University. Studied incidentally at 

 first, these new forms were later given special attention. About nine 

 thousand plants, of which about two thousand were progeny of 

 mutant-type parents of peculiar heredity (nearly one-fourth of the 

 latter representing crosses with Snowflake), have been examined 

 altogether. Some of these plants have been grown at Riverside, where 

 hybridization studies with mutant types are in progress. The present 

 account considers the origin and characteristics of these types, their 

 inheritance with self pollination, and the rather meager available data 

 relating to their behavior in crossing. 



In connection with the work at Cornell, special acknowledgment 

 is due to the late Professor John Craig, and to Dr. H. J. Webber 

 and Dr. H. H. Love. Facilities for work w^ere furnished by the depart- 

 ments of Horticulture and Plant Breeding of the New York State 

 College of Agriculture. 



GENETIC LITERATURE RELATING TO MATTTIIOLA 



The work of Correns (1900) on Mattliiola furnished one of the 

 earliest confirmations of Mendel's law, and also pointed to complica- 

 tions not found by ^Mendel. The earlier literature, according to Correns, 

 gives no indication of the study of Mattliiola hybrids beyond the first 

 generation. 



In his later paper on aberrant hybrid ratios, the same author 

 (1902) discusses complications in maize and in Mattliiola. After 

 referring the deviations found in maize to selective pollination, he 

 considers a suggestion of de Vries relating to environmental modi- 

 fication of Mendelian ratios, and himself suggests the possibility of 

 selective elimination of gametes. He says (pp. 171-172), "Solche 

 Einfliisse brauchten nicht alle Sorten Keimzellen des Bastardes gleich- 

 massig zu treffen, sondern sie konnten eine Sorte starker angreifen als 

 die andere." 



Von Tschermak (1904, 1912) has made extensive studies of 

 Mattliiola hybrids, considering mainly, as did Correns, pubescence and 

 flower color. The latter of these papers on hybrid.s in the genera 

 Mattliiola, Pisum, and Pltaseolus represents a careful analytical test 

 of the "factor hypothesis" of segregating inheritance, leading to the 

 conclusion that the applicability of this hypothesis is strongly con- 



