180 BOTANICAL GAZETTE [MARCH 
It was impossible to study the F generation because crosses between 
two F, individuals alike somatically would be without meaning, 
since nothing could be known of the gametic potentiality of each. 
Crosses between F, individuals, on the other hand, meant some- 
thing, because they were alike gametically. Six F, crosses were 
made therefore, and from them were grown 828 plants. 
TABLE I 
FREQUENCY DISTRIBUTIONS FOR LENGTH OF COROLLA IN A CROSS BETWEEN Nicotiana 
forgetiana AND N. alata grandiflora 
Class centers in millimeters 
Designation eae 
20 | 25 | 30| 35| 40] 45 | 50| 55 | 60| 65 | 70] 75 | 80) 85 | 99 
+5 oi Seemgeaiay fei cs. Eons ee a Gs SO i a ar) Chiat Remy Cantar Geir emery ar 
DSU Oe acai ys Ouray ew gee ee ba clea locales ifs] TO} 50] 50 Bale 
(pos Peony mee She pe aS satay (ies eteta “oles Cours Boras pokey a 
¥, taX3et) 1-6... .-| 5] 27] 79|136|125|132|102|r05) 64) 30] 15) 6} 2) -- 
Table I shows the frequency distribution for length of corolla 
of N. forgetiana (314) inbred, N. alata grandiflora (321) inbred, the 
F, generation (314X321), and the F, generation (314X321) 1-6. 
The measurement was taken from the end of the pedicel to the 
center of the contraction commonly known as the corolla throat. 
The classes have a magnitude of 5 mm. and are centered at the 
even centimeters and half-centimeters. A glance at the distributions 
themselves is sufficient to show the small variability of the parent 
types and of the F, generation, and the great variability of the F. 
generation. The F, generation is strictly intermediate, as is the 
mean of the F, generation. Among the individuals of the F., genera- 
tion, however, are flowers identical with each parent. This last fact is 
perhaps more clearly shown in the figures of pls. [X and X. 
The statistical constants for each frequency distribution are 
shown in table IT 
The spread of the corolla, measured to the tips of alternate 
lobes, behaved in the same way. Corolla breadth in N. forgetiana 
varied from 25-35 mm., with a sharp mode at 30 mm. The corolla 
spread of NV. alata grandiflora was somewhat more variable in terms 
of the arithmetical standard, ranging from 55 mm. to 80 mm. 
The range of the F, individuals extended from 45 mm. to 55 mm. 
