336 
GENETICS: GOODSPEED AND CLAUSEN 
year on their own roots, were measured at the beginning of the flowering 
season during the period from May 21 to June 20. During this time the 
flower size did not decrease as is shown by comparing the mean spread 
on the first dates of 38.81 =t 0.31 mm. with 40.05 =»= 0.35 mm., the mean 
spread for the last dates, and in the case of length of corolla, 55.19 =±= 0.15 
mm. and 53.81 0.24 mm., a slight decrease. On Plant 6, however, 
flowers were measured again on July 31. It was found that a mean 
spread of 43.41 mm. based on measurements of all the flowers on June 
16 had decreased to 37.38 mm. based on measurements of all the flowers 
on July 31. H44, which was measured during this same period, similarly 
shows only a slight decrease in flower size, but in every case where 
flowers were measured on the later date a striking decrease in size was 
obtained. We have taken the results of similar determinations and con- 
densed them in the following table in which not only the means and 
their probable errors are given, but also the differences between measure- 
ments of different dates and the probable errors of these differences. 
These differences are to be regarded as significant in case they exceed 
two and a half or three times the corresponding probable error. In 
each case the constant for spread is given on the first line, that for 
length on the second. 
Influence of Age of Plant on Flower Size. Measures in Millimeters 
MEANS FOR DATES 
DIFFERENCES BETWEEN DATES 
GARDEN 
NUMBER 
First 
Mid 
Last 
First and Mid 
Mid and Last 
First and Last 
13F,H« 
38.53 =t 0.38 
40.16 ± 0.44 
39.32 ± 0.64 
-1.63 =t 0.58 
0.84 ± 0.77 
-0.79 ± 0.74 
54 
05 ± 0.26 
54.53 ± 0.28 
52.84 ± 0.49 
-0.48 ± 0.39 
1.69 ± 0.57 
1.21 =fc 0.56 
13FiH 38 
38 
81 ± 0.31 
39.05 =fc 0.40 
40.05 ± 0.35 
-0.24 ± 0.51 
-1.00 ± 0.53 
-1.24 ± 0.47 
55 
19 =t 0.15 
55.43 ± 0.15 
53.81 ± 0.24 
-0.24 ± 0.21 
1.62 ± 0.28 
1.38 0.28 
13fll)FiH3S 
39 
10 =fc 0.31 
36.10 =t 0.43 
33.10 =fc 0.22 
3.00 =*= 0.53 
3.00 ± 0.49 
6.00 ± 0.38 
57 
10 ± 0.22 
54.10 ± 0.29 
52.60 =t 0.29 
3.00 ± 0.37 
1.50 ± 0.41 
4.50 ± 0.37 
13FiHi37 
38 
83 ± 0.11 
36.67 ± 0.44 
31.67 ± 0.26 
1.66 ± 0.45 
5.00 ± 0.51 
6.66 =fc 0.28 
56 
22 d= 0.09 
55.00 ± 0.18 
53.44 ± 0.28 
1.22 ± 0.21 
1.56 ± 0.34 
2.78 ± 0.30 
13 22/07 
28 
48 ± 0.09 
24.19 =fc 0.22 
4.29 ± 0.24 
45.60 ± 0.07 
42.25 ± 0.15 
3.35 ± 0.17 
With respect to the influence of removal of flowers on corolla size, 
the measurements show a striking correspondence between the size of 
corolla and the presence of developing seed capsules on the plant. By 
removing all flowers from the plant as fast as they go by it is possible 
to keep up the flower size to nearly that of the first flowers produced, 
and in some cases to double the life of the plant. A case in point is 
that of two plants of the N. Tabacum var. macro phylla series. On Plant 
14 only the flowers measured were removed, while on Plant 15 all flowers 
