136 
AGRICULTURE: REED AND HOLLAND 
sunflower was chosen for this work because of the fact that it grows without 
producing branches and it was thought that measurements of growth and weight 
represented the growth of the entire organism with a fair degree of accuracy. 
The adjacent plants were removed from the vicinity of those selected so that 
there was space of about 20 centimeters between any plant and its nearest 
neighbor. In short, environmental conditions were made as nearly uniform 
for the individuals in this small group as it was feasible to make them under 
field conditions. In the latter part of July the terminal buds began to de- 
velop into blossoms and coincidentally the plants ceased to elongate. 
The plants used in these studies were evidently of mixed ancestry as 
shown by the presence of branched and unbranched individuals. The seed 
had been bought at a seedstore and nothing was known of its pedigree. 
The branching habit is regarded by Shull (1908) to be a Mendelian character. 
TABLE 1 
Constants for Growth and Variation in Height of Helianthus- Plants 
DAYS 
MEAN HEIGHT 
INCREASE OF MEAN 
HEIGHT 
STANDARD DEVIATION 
COEFFICIENT OF 
VARIABILITY 
cm. 
cm. 
7 
17.93± 0.14 
7.93=±= 0.14 
1.62 =±= 1.01 
9.03=1= 0.56 
14 
36.36± 0.43 
18.43 =t 0.43 . 
4.83 =±= 0.30 
13.28=1= 0.85 
21 
67.76=t 0.78 
31.40=t 0.89 
8.93=1= 0.56 
13.17 =±= 0.84 
28 
98.10=t 1.38 
30.34 =t 1.59 
15.60± 0.98 
15.90 ± 1.02 
35 
131. 00 ± 1.73 
32.90=1= 2.21 
19.52=1= 1.22 
14.90 =t 0.95 
42 
169. 50± 2.21 
38.50=1= 2.81 
25.00 =t 1.56 
14.75=1= 0.94 
49 
205.50 ± 2.92 
36.00=1= 3.66 
33.00=1= 2.07 
16.06 ± 1.03 
56 
228. 30± 3.41 
22.80=t= 4.49 
38.47 =1= 2.41 
16.84=1= 1.08 
63 
247.10=1= 3.80 
18.80=1= 5.10 
42.92 =t 2.69 
17.38=1= 1.12 
70 
250.50=t 3.76 
3.40 =±= 5.35 
42.48=1= 2.66 
16.95=1= 1.09 
77 
253.80 =t 3.99 
3.30 ± 5.48 
45.06=1= 2.82 
17.75=t 1.13 
84 
254.50 =t 3.89 
0.70=1= 5.57 
43.90=1= 2.75 
17.25=t 1.11 
One importatit difference should be noted between the plants described by 
Shull and those in our series, viz: Shull's plants branched from the lower 
nodes of the stalk, while ours branched only from the upper nodes. Church 
(1915) regards the branched form as a mutant of the unbranched and believes 
that it is the oldest mutation on record. 
The branched form usually produces a head on the apex of each branch, 
whereas the unbranched form produces one head from the apical bud of the 
stem and no other. 
This mixture of branched and unbranched stems is not thought to affect 
the validity of the measurements upon which the present study is based, 
since only seventeen out of the fifty-eight plants were branched. The av- 
erage heights of the two classes at maturity were close enough together to 
be within the range of the probable error, though the length of the average 
growing season of the branched plants was 4.6 days longer than that of the 
