308 University of California l^uhlications in Botany [Vol. 5 



flowers of the F^ in plate 45, figure 1, were, on the other hand, picked 

 out to show the range of expression of the ealycine flower type and to 

 demonstrate that even those flowers which on superficial examination 

 appear to be normally developed actually exhibit a trace of the 

 petaloid abnormality in the calyx. Thus, the calyx of the flower in 

 the upper right-hand corner of plate 45, figure 1, has an indistinct 

 streak of light-colored tissue at the point where the pin is seen to 

 pass through the flower. The two flowers below show increasing 

 amounts of this petaloid tissue. Now calycina bears many flowers 

 with only this slight amount of petaloidy of the calyx and figures 

 1 and 2 of plate 45 might be combined to represent the total range 

 of floral abnormality in calycina and in the F^ also. However, the 

 flowers shown in figure 1 are representative of the majority of the 

 Fj flowers, while those shown in figure 2 are correspondingly repre- 

 sentative of the majority of the flowers of calycina. A number of 

 varietal hybrids in which calycina has been crossed with other 

 Tahacum varieties have been grown through many generations. In 

 these hybrids the calycine-flower character is recessive to normal 

 flower. In the species hybrids, on the other hand, the calycine-flower 

 factor of the dominant Tahacum reaction system which is acting as 

 a unit permits the otherwise recessive calycine-flower character to be 

 manifested in Fj. Flower color in calycina and F^ H40 is the same, 

 and varies from light red to bright pink. The corolla limb proper 

 is light red and this color may run in streaks down the corolla tube, 

 while the petaloid calyx may be entirely colored or partially green. 

 Habit and leaf characters peculiar to calycina are strikingly repro- 

 duced in the hybrid, as shown in plate 39, figure 2. 



F,H142— N. Tabacum "Maryland" X N. sylvestris 



This hybrid and its parents are figured in plate 40, plate 41, plate 

 44, figure 2, and in plate 48. FjH142 is the most vigorous of all 

 the various hybrids herein descriljed. It overtops both its parents 

 as must as three feet in many cases, and is correspondingly luxuriant 

 as to vegetative and floral characters. In general habit "Maryland" 

 and the F, are remarkably similar in that each shows a pyramidal 

 or conical shape due to the large spreading basal leaves and the rapid 

 diminution of leaf size as one passes up the main axis. This habit 

 is especially well seen in the row of FiH142 in plate 40. figure 1, and 

 also in plate 41, figure 2, whereas the single plant of "Maryland," 

 shown in plate 41, figure 1, is overmature and the large laterals pro- 



