18 BULLETIN 1484, U. S. DEPARTMENT OF AGRICULTURE 
holes left by the removal of a plant and not refilled with soil, showed 
a marked degree of recovery by October and produced several bolls 
of normal size late in the season. It is believed that the additional 
moisture supplied by the water collected in this hole during irrigations 
influenced this recovery. 
From these observations it seems apparent that increasing the 
water supply of the plants alleviated the conditions which induced 
the symptoms of crazy-top, and that the causal agent, if an organism, 
has the relation of a weak virus or parasite which has little or no 
effect upon the plants when favorable growing conditions exist. 
INOCULATION EXPERIMENTS 
In August, 1923, an attempt was made to determine whether the 
crazy-top disorder could be transmitted by injection of the sap from 
diseased tissues into healthy plants as is possible in some of the mo- 
saic diseases. About 100 cubic centimeters of tissue fluid was collected 
from the distorted leaves, petioles, and stsms of diseased Pima plants 
at the Sacaton seed farm and used for inoculation tests on 15 normal 
Pima plants in an area where no disease had occurred. The sap was 
rubbed into mutilations made on the roots, stems, leaves and growing 
buds of the healthy plants, but the later growth of all the plants was 
normal in every respect. 
On July 18, 1924, one of the writers performed similar tests on 16 
healthy plants in a field of Acala cotton near Casa Grande, Ariz. 
The inoculations were made under the direction of George L. Peltier, 
a pathologist of the Bureau of Plant Industry of the United States 
Department of Agriculture. Three or four cubic centimeters of the 
freshly expressed tissue fluid from diseased plants was injected by 
means of a hypodermic syringe into each of the growing terminal 
buds of 14 of the plants in the disease-free area. All of the leaves 
of two other plants in this area were rubbed with crushed leaves from 
diseased plants until mutilated. Although all of the 16 plants made 
a growth of 5 to 8 inches during the remainder of the season, no dis- 
ease symptoms appeared. 
In order to obtain evidence on the possibility of an organism or 
virus being transmitted by the soil, about 2Yi cubic feet of soil was 
removed from a severely diseased area in the Casa Grande Valley in 
1923 and transported to Sacaton, where it was packed into a trench 
tli at had been dug alongside several late-planted Hartsville cotton 
plants in an isolated area. The transported soil was placed in actual 
contact with a part of the root system of each plant, but no abnormal 
habits of growth resulted, nor was there any evidence of the disease 
in this area the following year. The results of these tests are not 
considered as conclusive regarding the nature of the disease, but they 
give further support to the view that the disease, if infectious, is not 
shown by plants under favorable growing conditions. 
PRACTICABILITY OF PREVENTION OR CONTROL 
From the information at hand it appears that the crazy-top disorder 
of cotton is readily responsive to control measures, since the cultural 
conditions exert such a marked influence on its symptoms. Rotation 
with alfalfa is definitely indicated as a practical measure by^the 
