1915] BARTLETT—MASS MUTATION 441 
varying degrees of mutability. The progenies of crosses indicate 
that mass mutability is conditioned by the female gametes. 
Mut. /atifolia.—In contrast with mut. angustifolia, mut. latifolia 
reproduces itself in part of its progeny. Its descendants include 
roughly 50 per cent f. typica and 50 per cent mut. Jatifolia, the 
proportion varying within rather wide limits. Moreover, mut. 
latifolia gives progenies of the same type whether self-pollinated or 
nee : 
Fic. 7.—Mut. sefacea: 2 mature plants from the F; progeny of f. typica, from F, 
parent Lexington E-s5; the right-hand plant, Lexington E-5-164, is shown also in fig. 5; 
note particularly the dimorphic foliage. 
cross-pollinated with f. typica. The reciprocal cross, with f. typica 
as the pistillate parent, consists only of f. typica, aside from the 
usual low proportion of mutations, among which mut. /atifolia may 
or may not happen to occur. These relations are as follows: 
mut. latifolia X mut. latifolia > f. typica+mut. latifolia 
mut. /atifoliaXf. typica—> f. typica+mut. latifolia 
f. typicaX mut. latifolia > f. typica 
