816 
Journal of Agricultural Research 
Vol. XXVIII, No. 8 
The extreme of crazy-top injury is shown in Plates 10 and 11 from a photograph 
of Hartsville cotton secured by Robert D. Martin in September, 1923, from 
badly affected areas that had been located by C. J. King in the field of Hartsville 
cotton near Casa Grande, Ariz. (See also PL 1.) At that time some of the 
plants had the leaves of the upper portion of the stalk reduced to mere rudiments 
or quite abortive. In that condition there was a notable similarity to the smalling 
disease in Haiti, as shown in Plate 9. The resemblance was recognized at once 
by A. T. Valentine, who reached Arizona in August after seeing the Haitian 
disease in July. Thus the similarity of the symptoms of the two diseases in 
Upland cotton led to a more detailed comparison of other features of crazy-top 
with the disorders that had been studied previously in Haiti and in China. 
Even when there is little or no distortion of the crazy-top leaves in Upland 
cotton, the size of the leaves may be greatly reduced, and the form of the leaves 
may be changed by broadening and shortening of the lobes, so that the outlines 
are much more rounded. (See PI. 12 and 13.) 
Some plants have much less reduction of leaves than others, though the leaves 
are of simplified shape, with the lobes only slightly developed. On the other 
hand, some plants have leaves very small, but without showing any tendency to 
reduce or suppress the lobes. Hence it may be inferred that the size and the 
shape of leaves are separate “characters.” In some of the late season growth as 
shown in Plate 14 the leaves are aborted, so that the top of the plant shows only 
bracts, or bracts and small flowers, sometimes in a dense cluster or a spike, with 
a complete absence of leaves. 
With Pima cotton there is a less obvious change in leaf-forms, but small simple 
leaves, as shown in Plate 3, are of more frequent occurrence on small crazy-top 
plants, at least where growth is restricted by less favorable cultural conditions. 
Thus the restriction of growth and the reduction of many of the leaves to simple 
form is in common with Upland cotton. 
LEAVES NOT DISCOLORED 
The lack of mottling or discoloration of the leaves is a peculiar feature of 
crazy-top, in view of the similarity in other respects to mosaic diseases. Even 
where the affected plants appear stunted and show many deformities of the 
leaves or other parts, the foliage is not discolored, and the crazy-top areas appear 
darker than the rest of the field at the end of the season, possibly because the 
plants are sterile and the foliage does not ripen as on the normal fruitful plants. 
However, it is known that other mosaic symptoms may occur without mottling 
of the leaves. In a mosaic disease of the potato, as reported recently by Mac¬ 
Millan (15), the mottling of the leaves does not appear in plants that are grown 
at high altitudes, 8,000 to 8,500 feet, in the Rocky Mountains. Thq,more intense 
sunlight of the high altitudes was found to be responsible for the disappearance 
of mottling, as proved by an experiment with plants grown in partial shade, 
which showed the usual discoloration of the leaves. 
A recent account of a growth disorder of strawberries describes the leaves and 
inflorescences as greatly reduced and distorted, with no indication of mosaic 
discoloration, although under some conditions a marked reddening of the surfaces 
may appear. This disorder is supposed to be due to nematodes that are found in 
the terminal buds of the abnormal strawberry plants ( 1 ). 
Though the color is not altered, the texture of the leaves in crazy-top appears 
to be slightly firmer and more brittle. A difference of behavior was noted by 
Robert D. Martin in crazy-top material collected and photographed in September 
and placed in water to keep fresh. It was noticed that the crazy-top growth did 
not revive, but soon shriveled and dried, although the stems were standing in 
