268 



Shull. 



the narrow-leafed and broad-leafed forms differ little in length, but the 

 rosette-leaves of angustifolia are usually less than half the width of those 

 of the ordinary "typica"- strains. The apexes in angustifolia are long- 

 acuminate, and often more or less curled into delicate hooks or loose 

 croziers, the normal form being only sharply acute, as seen in Plate I. 

 The adult leaves of angustifolia are generally of slightly firmer texture 

 than those of the "typica"- races, but a section of a leaf shows no very 



Fig. 1. Seedlings of Lychnis dioica from a cross between a heterozygous 



female and a narrow-leafed male sib (Fed. No. 12202). Photo Mar. 22, 1913. 



Oldest plants are 29 days old. The seed-pan is 30 cm broad. 



obvious difference in structure, except that the intercellular spaces among 

 the cells of the mesophyll are smaller in angustifolia, while the cells 

 themselves are not notably different in size, form or arrangement; con 

 sequently the difference in width of the leaves is mainly dependent or 

 a difference in the number of cell -divisions which take place in tht 

 transverse direction, while the number of cells in the longitudinal 

 tion is not much different from the number in the normal form. 



