NON-INHERITANCE OF TERMINAL BUD ABORTION IN 
PIMA COTTON 1 
By Thomas H. Kearney 
Physiologist irCJJharge , Alkali and Drought Resistant Plant Investigations , Bureau 
of Plant Industry , United States Department of Agriculture 
The normal development of the cotton plant is often interfered with, and 
various types^of malformation result. One of the most common and char¬ 
acteristic of these teratological states is associated with arrested development 
or abortion [of the terminal bud of the axis. The frequency of this phenome¬ 
non is indicated by the fact that of 1,109 plants of Pima cotton under obser¬ 
vation in 1918, 44, or approximately 4 per cent, had the terminal bud aborted. 
In a majority of Cases the injury occurs during the seedling stage, 35 of the 
44 individuals having shown abortion at the time the cotton was thinned. Yet 
the terminal bud may be lost at any time during the growth of the plant. An 
individual in which the injury occurred at a comparatively late stage of develop., 
ment is shown in Plate 1, with an adjacent, uninjured plant for comparison. 
The cause of abortion of the terminal bud is not known, although the injury is 
frequently associated with leaf-cut or tomosis, 2 and indications of injury by the 
larvae of an insect were observed in one case. If it occurs early in the life of 
the plant, one of the vegetative branches produced at low nodes of the axis may 
assume an erect position, simulating so closely a true axis that close observation 
is required to determine that the original growing point has been destroyed or 
arrested. If abortion takes place in a later stage of development, as in the indi¬ 
vidual shown in Plate 1, the fruiting branches just below the point of injury 
become elongated and often branched, with a tendency to assume a more nearly 
erect position and to produce abnormally large leaves of coarse texture. The 
same phenomenon may be induced by artificially “topping’’ the plant. 
As in all such cases, it is important to know whether we are dealing with a 
heritable character. If this malformation is inherited, aborted individuals 
should be removed in roguing seed-increase fields, for they are nearly always les& 
fruitful than normal plants. In an endeavor to solve this problem, 12 aborted 
individuals of the Pima variety of Egyptian cotton, as well as 12 normal indi¬ 
viduals to serve as controls, were selected at the United States Field Station, 
Sacaton, Ariz. The control for each aborted plant was either the next plant in 
the row or the nearest normal plant that could be found. Each aborted plant 
and its control were given the same number. Flowers on all of the aborted and 
normal individuals were bagged to prevent cross-pollination and from the result¬ 
ing self-fertilized seed progenies of the 24 plants were grown the following year. 
Each pair of progenies representing a normal and an aborted plant were located 
in the same portion of the field, so as to reduce to a minimum the influence of 
soil heterogeneity. 
1 Received for publication April 9, 1924—issued Nov., 1924. 
2 Cook, O. F. leaf-cut, or tomosis, a disorder of cotton seedlings. U. S. Dept. Agr. Bur. Plant 
Indus. Circ. 120: 29-34, illus. 1913. 
Journal of Agricultural Research, 
Washington, D. C. 
( 1041 ) 
Vol. XXVIII, No. 10 
June 7, 1924 
Key No. G-419 
