S. DEPARTMENT OF AGRICULTURE. 
of Holdon and of Pima were also grown in 1918 from self -fertilized 
seed of plants in the corresponding progenies of 1917. 
In 1919 F 2 progenies were grown from each of 3 ¥ 1 individuals of 
1918, the three progenies having comprised, respectively, 69, 95, and 
51 individuals. An F x progeny, the parents of which were a single 
individual in the selfed Holdon and a single individual in the selfed 
Pima progeny of 1917, was also planted, but great difficulty was 
experienced in obtaining a stand and only 5 individuals survived. 
Like difficulty occurred with the parental progenies grown in 1919, 
only 15 plants of Holdon and 13 plants of Pima having survived. 
Fortunately, the magnitude of the difference between these varieties in 
respect to most of the characters made the small size of the parental 
progenies a less serious disadvantage than would otherwise have been 
the case for the purpose of comparison with the hybrid. 
The Holdon progeny was from self -fertilized seed produced by a 
plant in the population of 1917. The Pima progeny was from self- 
fertilized seed produced by a plant in the progeny of 1918. The 
Holdon parental progeny of 1919 was in the second generation of 
strict self-fertilization, and the Pima parental progeny of 1919 was 
in the fifth self-fertilized generation. For the sake of brevity these 
Holdon and Pima populations will be referred to hereafter as the 
" parental populations" regardless of what generation of the hybrid 
is being compared with them. 
In 1920 F 3 progenies of 48 individuals in the F 2 of 1919 were grown. 
Of the F 3 progenies 13 were from self -fertilized seed only, 21 
comprised plants from both self-fertilized and open-pollinated seed, 
and 14 (the F 2 parents of which had matured no bolls from strictly 
self-fertilized flowers) were grown from open-pollinated seed only. 5 
An Fj of 24 individuals, obtained by cross-pollinating, in 1919, 
flowers on a plant in the Holdon parental progeny with pollen from 
a plant in the Pima parental progeny, was grown in 1920. The 
Holdon and Pima populations grown in 1920 were unfortunately 
situated in strong alkali soil, and the plants were so stunted that they 
could not be used for comparison with the hybrids. 
CHARACTERS DISTINGUISHING THE HOLDON AND PIMA VARIETIES. 
Some of the more important characters distinguishing the Holdon 
variety from the Pima are summarized in the following, paragraphs. 
Many of these characters are also diagnostic as between the upland 
and Egyptian types of cotton in general. Differences which lend 
themselves to direct measurement or grading are indicated by 
comparison of the means in Table 1. 
Stem and branch characters (PI. I). — Pima, as compared with 
Holdon, has a much taller axis with longer and more numerous 
internodes. The fruiting branches of Pima are very much longer 
and have very much longer internodes than those of Holdon. In the 
first generation of the hybrid (PI. II) the type of plant is intermediate i 
but shows a marked degree of heterosis or hybrid vigor. 
& No rneasurements of characters were made on progenies grown from open-pollinated seed only with 
the exception of No. 161 , in which about one-third of the plants were so similar in all their characters and 
corresponded so closely to the description of the F 2 parent as to leave no reasonable doubt of their 
derivation from self-fertilized ovules. In four of the progenies, which comprised both selfed and open- 
pollinated plants, the number of the former having been too small to furnish satisfactory statistical 
constants, measurements were also made upon such of the individuals from open-pollinated seed as 
showed, by comparison with the individuals resulting from controlled self-fertilization, that they, too, 
were presumably the product of self-fertilized ovules. 
