HYBRID OF DIGITALIS. 



369 



that the means of the hybrid and of luted happen to be rather 

 -close together, but nevertheless even here the distribution of the 

 baekcross offspring indicates a homogeneous series. 



Leaf: Length of Guard-cells of Stomates. — The stomates 

 of lutea are much larger than those of gloxiniceflora. The length 

 of the guard-cells in the hybrids is very variable, and the mean 

 (72) is intermediate between that of hi tea (84) and that of 

 gloxiniozflora (60). The variability exceeds that of either of the 

 parent species. The mean of the gloxiniceflora baekcross (71) is 

 very much nearer to the hybrid mean (72) than to the glox. mean 

 (60), and the mean of the lutea baekcross (80) is much nearer to 

 the lutea mean (84) than to the hybrid mean (72). 



Length of Guard-Cells of Stomates of Lower Surface of Leaf. 



Grades of lengths 



in divisions 



(0041 nun.) of oculai- 



micrometer x 10 



PP 



o-t- *X) 



=q^' 



PY x PP 



m en- <X> 



FY 



y *o 





PY x YY 



YY 



50 53 



54—57 

 58—61 

 62—65 

 66—69 



70—73 

 74-77 

 78—81 

 82—85 

 86—89 

 90—93 

 94—97 

 98—101 



Means 



5 

 13 



6 

 2 



60 



Reference to the 3rd column shows that there is no tendency 

 for the offspring of the gloxiniceflora baekcross to cluster around 

 the mean of gloxiniceflora (grade 58-61). With the lutea back- 

 cross the condition is not clear on account of the fact that the 

 hybrid baekcross and lutea means are too close together. 



Leaf : Ratio of Breadth to Length. — Relative to the 

 length, the leaves of lutea tend to be very much narrower than 

 those of gloxiniceflora (PI. IV, fig. 2). In the hybrid the mean (244) 

 of the ratios is closer to that of gloxiniceflora (285) than to that of 

 lutea (160). The mean of the glox. baekcross (297) is much nearer 

 to the glox. mean (285) than to the hybrid mean (244), and the 

 mean of the lutea baekcross (181) is much nearer to the Infect, 

 mean (160) than to the hybrid mean (244), 



