298 Shull. 



both possess in common is nearly all of that which they each possess, 

 and that the additional element or elements which are required for 

 the actual realization of the one or the other sex, are conceivably of 

 relatively minor value. 



Summary. 



The discovery by BAUR of a narrow -leafed mutant in Lychnis 

 dioica has led to the demonstration that the relatively broad leaves of 

 the normal or "typica" form is a sex-limited character. 



This narrow- leafed form is here described and illustrated under 

 the name Lychnis dioica angustifolia. It differs from the normal type 

 not only in its narrow leaves, but also in having narrower petals and 

 longer rudimentary ovaries. 



In crosses with the normal type angustifolia is a recessive which 

 reappears in the F 2 only in half of the males. A complete analysis of 

 the Fs family showed that all of the broad -leafed males were hetero- 

 zygous for the broad -leaf factor 5, and that half of the females were 

 homozygous, and half heterozygous, for the same factor. This confirms 

 the conclusion gained from the breeding of hermaphrodites, that the female 

 of Lychnis dioica is a sex-hoinozygote and the male a sex-heterozygote. 



There was a remarkable absence of females in families produced 

 by matings between. the F 2 narrow-leafed males and numerous females; 

 the total progenies from such matings included 2741 males and only 

 14 females, and 8 of the latter occurred in one small family of 66 indi- 

 viduals. The broad-leafed males in the same F 2 family produced males 

 and females in approximately equal numbers. 



The F 2 families resulting from crosses between heterozygous females 

 and narrow -leafed males were expected to produce about 25 per cent 

 narrow-leafed females. Only 2 females appeared in such families among 

 a total progeny of 1097 and these 2 happened to be broad-leafed. 



One narrow-leafed female did appear, but in a family in which it 

 was not expected, having been produced by a cross between a hetero- 

 zygous female and a broad-leafed male. This female was a very small 

 dwarf; its genotypic relationship to the angustifolia form is unknown. 



Evidence is presented indicating that the males of normal strains 

 not directly related to the original angustifolia mutant, are heterozygous 

 for the broad -leaf gene B, but further investigation will be necessary 

 to determine whether this is generally the case. 



The hermaphroditic plants in families derived from my original 

 hermaphroditic mutants are also heterozygous for the gene B, which 



