268 



Shull. 



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

 rosette-leaves of angustifolia are usuall}' less than half the width of those 

 of the ordinary- "typica'-siv&m?,. The apexes in angustifolia are loug- 

 acuniinate, 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 "^?/^2ca"-races, but a section of a leaf shows no very 









Fig. 1. Seeiiliugs (if Lijchnif: rliinca troni a rross 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 .'SO cm broad. 



obvious difference in structure, except that the interctiliular spaces among 

 the cells of the niesopliyll 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 de])endeut on 

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

 transverse direction, while the number of cells in the longitudinal direc- 

 tion is not mucli different finm the number in the ndrmal fdrm. 



