MUTATION IN MATTHIOLA 



283 



6. THE NAREOW-LEAVED TYPE 



As table 37 indicates, this type competes with crenate for second 

 place in frequency of occurrence in the Ithaca cultures ; in fact, when 

 only the strictly unselected cultures are considered the percentage is 

 very close to that for smooth-leaved. A feature of special interest is 

 the apparent association of the mutant type with doubleness. 



In a cool greenhouse this type (fig. 22) varied from exceptionally 

 late and many-noded to ordinary in both characters. The leaves (see 

 also fig. 18) were typically narrow, rather strictly entire, often rolled 

 backward or twisted, and typically more ascending than those of 



TABLE 37 



Narrow-leaved type. Numbers of apparent mutants and association of the type 

 with doubleness of flowers. 



a See note b to table 2. 

 b See note c to table 1. 



Snowflake. The apex of the leaf is often more acute than with Snow- 

 flake, and many leaves are mucronate or at least end in a sharp, rigid 

 tip. 



A striking characteristic is the narrowness of the sepals, resulting 

 in frequent early separation at the edges, partially exposing the petals 

 in immature buds. 



Under the less favorable field conditions the plants often remain 

 long as dwarf rosettes, and flower late and feebly if at all. Figures 23 

 and 24 show comparatively well developed plants in the field. 



The type is on the whole very distinct in the field, though there 

 has been some question whether a greenhouse plant such as that in 

 figure 18 is genetically different from those with short and rigid 

 leaves (figs. 22 and 24) ; the very great variability in leaf form due 

 to external conditions makes such a question very difficult without 

 extensive progeny tests. It is now (1918) probable that narrow-dark 

 (p. 143) was not distinguished from narrow in the greenhouse. 



[141] 



