May 24, 1924 
Acromania, or u Crazy-Top” 
809 
continue much later in the season, so that the plants may not recover in time 
to mature a full crop. The deformity and mutilation of the leaves were still 
severe in the Sea Island cotton after adjoining rows of Pima cotton had entirely 
recovered. Upland cottons also suffer severely from tomosis, and may be 
outgrown and outyielded by the Egyptian cotton, under conditions in the South¬ 
west. 
HYBOSIS, OR LEAP-CURL 
The chief symptoms of hybosis are reduction and distortion of the leaves, but 
without the perforations or mutilations which are characteristic of tomosis. 
The two disorders are commonly found together on the same plant or on the 
same leaf, but may also occur separately (4). 
The hybosis distortion is an upward swelling or crumpling of the tissue of the 
leaves, and usually is greater between the principal veins near the base of the 
leaf. The plant lice producing the injuries shown in Plate 6 were identified as 
Aphis gossypii Glover, a species that is widely distributed. Plant lice are 
regularly present with hybosis, and apparently are the cause of this disorder, 
though the extent of the malformations of the leaves depends upon the tempera¬ 
ture as well as upon the presence of the insects. 
The greatest malformations occur during the cool weather of the spring months, 
when the cotton is making only a slow growth (PL 6). As soon as the weather 
is warm enough for the cotton to grow rapidly the growth becomes normal. 
The altered behavior of the plants may be ascribed to the warmer weather, since 
the plant lice may still be present, though usually they become less numerous 
in midseason, and increase again in the fall. Also the hybosis symptoms return 
as the weather becomes cooler. 
In some cases the recovery from hybosis is not uniform, and the growth of the 
plants in definitely restricted spots or areas may continue to show severe hybosis 
injuries while over the rest of the field the plants are producing normal leaves. 
Such irregularities were noted in fields of Pima cotton in the Salt River Valley, 
June 28, 1920, and a photograph secured which show r s the extent of the hybosis 
deformity, continued later in the season than usual. No reason was found for the 
striking difference of behavior. The suggestion of alkali spots was considered, but 
seemed improbable. The possibility that such plants had been infected with 
crazv-top or some other disorder, which could intensify the hybosis effect, may 
be worthy of consideration. 
The appearance of late-season hybosis in Mebane cotton at Sacaton, Ariz., in 
November, 1923, is shown in Plate 7. The internodes are much shortened and the 
leaves crumpled, though the size of the leaves and of the involucral bracts is not 
much reduced, and there are gradual changes from the normal to the distorted 
condition. Thus it is easy to distinguish the late-season hybosis from crazy-top, 
although from a distance the two might be confused. Hybosis is likely to be 
accompanied by tomosis, which is true also of crazy-top. The lacerated leaf at the 
lower right-hand corner of Plate 7 may be an example of tomosis, or possibly of 
insect injury. The plant lice were quite numerous on the specimen photographed, 
and of a very dark greenish color. 
Hybosis is a prominent feature in the black-land prairie region of Texas, which 
is now the chief center of cotton production in the United States. The surface 
soil of the black-land prairies is likely to be wet and cold in the spring, and the 
growth of the cotton may be restricted for several weeks by a heavy infestation 
of plant lice, and the resulting distortion of the leaves may be very severe, though 
without a permanent injury to the crop. On the contrary, many farmers believe 
that it is good for the cotton to become “lousy ” in the early stages. The restric¬ 
tion of growth early in the season is really an advantage under the black-land 
