1919] Frost: Mntation in Matthiola 85 



firmed by the results secured. This work, with that of Miss Saunders, 

 leaves no possibility of doubt that the typical Mendelian mechanism is 

 present in Matthiola. 



The most extensive genetic work on Matthiola is evidently that of 

 Miss Saunders, reported by herself (1911, 1911a, 1913, 1913a, 1915, 

 1916) and by Bateson and Saunders, with others (1902, 1905, 1906, 

 1908). This also is work on heredity in hybrids, with special emphasis 

 on the factorial interpretation of the various complications relating 

 to pubescence and to "doubleness" of flowers. 



Goldschmidt (1913) has explained the inheritance of doubleness 

 by sex linkage and lethal action of a femaleness factor in pollen 

 formation, and his interpretation has been criticized by Miss Saunders 

 (1913). I (Fro.st, 1915) have presented a somewhat different lethal- 

 factor scheme, and Miss Saunders (1916) has since restated her views 

 and criticized mine. 



Muller (1917) has cited the inheritance of doubleness as a case of 

 "balanced factors," in apparent agreement with my formulation. 



Apparently no one but the present writer (Frost, 1912, 1916; see 

 also review by Bartlett, 1917) has reported experimental evidence of 

 any notable tendency to apparent mutation in the genus, although 

 de Vries (1906, p. 338) mentions the occasional occurrence of vigorous, 

 rigidly upright individuals (a gigas type?), known at Erfurt as 

 "generals," and refers to the rare mutative occurrence of single 

 flowers on branches of double-flowering plants. Doubleness, and color 

 variations in considerable number, have evidently arisen under culti- 

 vation, probably through mutative changes. 



METHODS 



The general cultural methods employed for the first three genera- 

 tions have been very briefly described elsewhere (Frost, 1911). 



The plants of the first four years were grown in pots in the green- 

 house. The plants of the first generation came from one or both of 

 two packets of commercial seed planted in the fall of 1906, and all 

 plants in the later cultures (possibly excepting series 18) were 

 descendants of these. The cultures will in general be designated by 

 the year in which the seed was sown ; the field and greenhouse cultures 

 of 1911 are indicated by 1911F and 1911 H respectively. 



Part of the seed planted, especially in 1908, came from unguarded 

 flowers. The seed lots where this occurred will be indicated in the 



