Feb. 9,1924 
Selective Fertilization in Cotton 
337 
tion could be obtained with this material, but it was thought advisable 
to test the possibility by experiment. 
In comparing cotton with maize ih respect to differential fertilization, 
the distinction applies which was made by Jones in comparing the results 
of Correns with Melandrium and his own results with maize. “In the 
former the pollen tubes enter the ovary at a common point and are free 
to fertilize the first ovules they reach. The tubes which grow fastest, 
therefore, fertilize the ovules in the upper part of the ovary, leaving the 
slower-growing tubes to pass on down to the lower part. In Zea each 
ovule has a separate style, so that the longer the distance to traverse is, 
the less chance will the slower-growing tubes have of reaching the goal 
first” (6, p . 173). Since cotton resembles Melandrium rather than 
Zea in these points of structure, we should expect to find a greater pro¬ 
portion of cross-fertilized ovules in the lower than in the upper part of 
the ovary, if the tubes of the like pollen grow more rapidly than the 
unlike pollen tubes. 
All bolls resulting from the double-pollination of Pima and Upland 
flowers in the two experiments described in the first part of this paper 
were halved when ripe and the seeds from the upper and from the lower 
halves were planted separately. (See p. 331.) The per centages of hy¬ 
brids from upper and from lower seeds are stated in Table V, the popula¬ 
tions from pollination with like + unlike and with unlike + like pollen 
having been taken as one array for each type of cotton in each experiment. 
Table V .—Percentages of hybrids in populations grown from seeds from the upper and 
from the lower halves of bolls produced by double-pollinated flowers of Pima and of 
Upland cotton 
Experiment and pollination. 
Half of boll furnishing 
seed for planting. 
Number of— 
Percentage 
of hybrids. 
Plants. 
Hybrids. 
EXPERIMENT I 
Pima with Pima and bone Star.. 
Upper. 
700 
227 
32. 4±l. 19 
Do. 
bower. 
681 
215 
31. 6± 1. 20 
Difference.... 
0. 8±i. 69 
EXPERIMENT 2 
Pima with Pima and Acala. 
Upper. 
4.0 C 
63 
15. 6±i. 21 
Do. 
bower. 
563 
100 
17. 8 db 1. 09 
Difference.... 
2. 2 - 4 - 1 . 63 
EXPERIMENT 1 
sm 
bone Star with bone Star and 
Upper. 
373 
86 
m 
23. o±i. 47 
Pima. 
Do. 
bower. 
379 
80 
21. ii 1. 41 
Difference.... 
I. 9±2. 04 
EXPERIMENT 2 
Acala with Acala and Pima. 
Upper. 
384 
123 
32 . O-h I. 60 
Do. 
bower. 
O'"'** - 
283 
97 
O w j- vv 
34 . 2 -t I. OO 
Difference.... 
2. 2±2. 48 
