214 GENETICS IN RELATION TO AGRICULTURE 
Shull’s conclusions are further supported by evidence from the 
inheritance of a sex-linked character in Lychnis, the only sex-linked 
character thus far known in plants. The character in question is that 
of narrow rosette leaves as distinguished from the normal broad type of 
leaf, and there are other associated character differences (Fig. 96). The 
narrow-leaved form, called angustifolia, was discovered by Baur as a 
single male mutant individual, a significant fact when taken in connection 
with its subsequent behavior. The factors in this case are B for the 
broad-leaved condition and 6 for the narrow-leaved condition. Crosses 
between typica females (BX)(BX), and angustifolia males (bX)Y 
Fie. 96.—Adult rosettes of Lychnis dioica; on the left a plant of the normal form, typica; 
on the right a plant of the narrow-leaved form, angustifolia. (After Shull.) 
gave in F’, all broad-leaved plants (BX)(bX) females and (BX)Y males. 
Heterozygous broad-leaved females (BX)(bX) mated to broad-leaved 
males (BX)Y gave all broad-leaved females, and approximately equal 
numbers of broad-leaved and narrow-leaved males. Hermaphrodites 
were also found to behave the same way with respect to the factor B 
as did the males, which confirms the hypothetical relation supposed to 
exist between hermaphrodites and females. The evidence clearly 
indicates the existence of sex-linkage of the kind called for on the assump- 
tion that Lychnis exhibits the X Y type of sex-inheritance. 
Secondary Sexual Characters.—Secondary sexual characters are 
those which appear as an invariable or almost invariable accompani- 
ment of a particular sex in most animal forms. They include many 
diverse things, such as the antlers in male deer, the horns of the males of 
some breeds of sheep, the mane of the lion, the power of song of many 
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