- 13 - 
in these locations especially that commercial fruit growers are 
largely dependent upon the honeybee — the only insect admirably 
adapted for pollinating fruit bloom that can be readily controlled 
by man. 
Kearney, T. H. 
1923. Self-fertilization and cross-fertilization in Pima cotton. U. S. 
Dept. Agr. Dept. Bui. 1134, 68 pp. 
p. 49x Observation in Arizona has shown that the number of 
efficient pollinating insects differs greatly in different localities . 2/ 
Bees and other active pollinators are normally abundant amon? the 
cotton flowers at Sacaton throughout the summer, and -the entire 
surface of the stigmas is almost invariably well covered with pollen 
soon after the corolla has opened. On the other hand, observations 
in the Salt River Valley, at distances of 25 to 4-0 miles from Sacaton, 
have shown that insect pollination of cotton there is often much less 
rapid and complete. The probable explanation is that in recent years 
an extensive and almost continuous acreage has been planted to cotton, 
and the insect population is not large enough to insure thorough 
pollination of all the flowers. 
Thus, on July 18, 1919, in a field situated near Tempe in the 
heart of the cotton-growing district, no pollen grains were observed 
upon the extrastaminal portion of the stigmas at 9 a.m. and very few 
at 10 a.m. late in the afternoon of July 20, 1920, inspection of the 
same field showed the extrastaminal portion of the stigmas to be 
free from pollen in most of the flowers, while the remaining bore only 
a few insect-transported grains. None of the flowers examined showed 
thorough pollination of the whole stigma tic surface. Two other cen- 
trally located fields, one at Phoenix and one near Tempe, which were 
examined at 5 p.m. on August 5 and at 4- p.m. on August 6, showed simi- 
larly deficient pollination. On the other hand, in fields situated 
on the outskirts of the valley, at Iitchfield and at Goodyear, which 
were examined at noon on the same days, bee3 and other pollinators 
were abundant, and the stigmas of the cotton flowers were found to be 
well covered with pollen. 
p. 50 : In the mean number of seeds per 100 flowers, a value 
which integrates the percentage of bolls matured and the mean number 
of^ seeds per boll, the increase due to artificial pollination amounted 
to* 32 per cent, indicating that a substantially greater crop both of 
seed and of fiber might be expected if bees were abundant in the Salt 
River Valley cotton fields during the blossoming period . 
2/ A pronounced difference in the abundance of pollinating insects at 
different localities in Arizona was noted by Cook, McLachlan, and Meade. n At 
the time of our visits to the fields at Yuma and Sacaton there was a notable 
difference in the activity of the insects at the two places. Several species 
of large wild bees that were industriously visiting the flowers at Yuma in 
September were not seen at all at Sacaton." 
