CRAZY-TOP DISORDER OF COTTON 11 
Other excavations were made where no material difference in the 
soil could be noted in trenches that extended from within the affected 
spots into the soil where the plants were normal in appearance, but 
in most cases when soil borings were made several feet distant from 
the worst affected spots, a change in the character of the soil was 
detected b} T the greater ease with which the borings were made. The 
root systems within affected areas were generally more abnormal than 
those of adjacent plants having normal tops, although the roots of 
the latter often were shallow and distorted, particularly in areas where 
the diseased plants were scattered. An extreme example of this was 
found in the field of Hartsville cotton near Casa Grande, referred to 
by Cook (2) and elsewhere alluded to in this paper, where crazy-top 
plants and near-by plants that appeared normal above ground were 
dug up iu September, 1924, and both types were found to have 
remarkably stunted root systems, no taproots having penetrated 
below a depth of 18 inches. This spot, noted in 1923 and 1924. was 
present in 1925 also, but the plants showed much less injury than in 
either of the previous years. The grower attributed this change to the 
different irrigation methods practiced in 1925, which allowed a greater 
amount of water to enter the soil. In the fail of 1925 several affected 
plants were removed from this field in cylindrical cores of earth about 
16 inches deep, and in no case had a taproot penetrated as far as the 
bottom of the core of earth. 
A considerable amount of study of the rooting habits of cotton 
plants in connection with this disorder has convinced the writers that 
there is a general tendency to shallow rooting in fields where crazy- 
top is prevalent. This is in contrast to the deep-rooting behavior of 
plants in alluvial soils where the disorder has never appeared. (PI. 3.) 
An interesting phenomenon was noted at the Sacaton seed farm in 
connection with the relation of the root system to the growth behav- 
ior of the plant. A plot which had been occupied by a few wide- 
spaced rows of alfalfa plants the preceding year was planted to Pima 
cotton in 1924, and by the middle of the summer crazy-top symptoms 
began to show in many plants. By autumn the disorder was more 
conspicuous, and it was observed that frequently a normal, well-fruited 
plant would be located between two plants severely affected with 
crazy-top and almost completely sterile. (PL 4, A.) In order to 
study the root development of the two types of plants, two pits were 
dug in this plot, one exposing the roots of two crazy-top plants with 
a normal plant between them, and another in which two normal 
plants alternated with two affected plants. The soil in this plot is 
a coarse sandy loam and was found to be very uniform in texture to 
a depth of about 4 feet, where it changed abruptly to a medium-fine 
sandy subsoil apparently much more retentive of moisture than the 
surface soil. The root systems of all the affected plants were found 
to be shallow and confined to the upper 2 y^ feet of soil and with 
poorly developed or aborted taproots, from which extended numerous 
lateral roots. The taproot of each of the three normal plants had 
entered the decayed taproot of an alfalfa plant of the previous season 
at a point below where the plow had cut it off, and each had descended 
into the subsoil through these old roots. The taproots of the normal 
plants also bore fewer lateral roots than did the crazv-top plants. 
(PL 4, B.) 
