188 BOTANICAL GAZETTE [MARCH 
7. Length of style and of filament are perfectly correlated with 
corolla length. 
8. Breadth of corolla shows an average correlation with length 
of corolla equal to 61 per cent. 
g. The frequency distribution of corolla length for the F, 
generation is positively skew. It is pointed out that the range 
of fluctuations of corolla length in the two pure species is twice 
as great in the one of larger size than in the other. Classes of 
equal size in frequency distributions of great variability appear to 
be arbitrary and improper, if size factors are assumed to be dynamic 
factors with fluctuations roughly expressed by the term growth 
force. To show this accelerative action, the class ranges must 
gradually increase as the size (that is, the number of factors) 
increases. It is shown that the distribution under discussion will 
be changed from skew to normal if a simple arithmetical increase 
in the size of the classes is made. 
Bussey INSTITUTION 
- Boston, Mass. 
" EXPLANATION OF PLATES 
PLATE Vi 
At the left, a young flowering plant of Nicotiana alata Link and Otto, vat- 
grandiflora Comes; at the right, a young flowering plant of NV. forgetiana Hort. 
Sand. 
PLATE VII 
A mature plant of the first hybrid generation of a cross between N. a 
getiana and N. alata grandiflora. 
> 
PLATE VIII 
Figs. I, 2, and 3, upper, Rete ea lower leaves of a mature plant of 
usaiela 
. PLATE: 1X 
At the left, a flower of NV. alata grandiflora; at the right, a flower of V- 
forgetiana; between them are extreme F, segregates in length and spread of 
corolla; taken on the same plate, three-fourths natural size. 
PLATE X 
Fig. 1, NV. alata grandiflora; fig. 2, N. forgetiana; fig. 3, cross between N. 
forgetiana a N. alata grandiflora, F; generation; the remaining figures are 
F, segregates; all figures are three-fourths natural size. 
