May 24, 1924 
Acromania, or u Crazy-Top" 
807 
dry, so that brachytic plants are sometimes considered as diseased on this 
account ( 5 ). 
As a morphological change, brachysm represents an acceleration or stepping 
forward in the course of development toward the fruiting stage, so that the 
normal differences between the internodes and the pedicels are reduced. It may 
be considered that the internode-pedicels of brachytic plants are formed by a 
process of metamer-hybridism, combining the characters of two successive 
structures that normally are distinct. In other words, there is a breaking down 
of the normal differentiation of the parts, or intermediate expression of the 
characters that are normally distinct, a type of variation to which the term 
metaphanic has been applied. 
Other metaphanic variations may be seen in the leaves of brachytic internodes 
which often are reduced and partially transformed into involucral bracts. Also 
the formation of the bracts is often abnormal in brachytic varieties, some bracts 
being more leaf-like, while others may be reduced and variously united with 
the calyx. 
Though brachysm is considered as a normal character of some of the Upland 
varieties, and such “cluster-cottons” may be very productive under favorable 
conditions, the brachytic habit is considered undesirable and to be avoided in 
breeding. The brachytic varieties generally are very unstable and the tend¬ 
ency to brachysm may be so intensified that many of the plants are completely 
sterile when cultural conditions are unfavorable. Thus brachysm reaches a 
destructive stage when the abortion of flower buds is increased, or is carried 
to the point of total abortion, resulting in complete sterility. This may occur 
in only a few individuals, or the sterile plants may be so numerous that the 
yield is greatly reduced. 
Various degrees of the brachytic tendency are shown. Some varieties that are 
not usually brachytic may have, under some conditions, very short fruiting 
branches. From the same stock of seed many brachytic plants may appear in 
some places, while in other places no indications of brachysm may be shown. 
In the Durango variety brachytic plants occur frequently in some of the irrigated 
valleys of Arizona and California, but may be quite absent in fields grown in 
South Carolina or in southern Virginia from the same stocks of seed, and similar 
behavior in relation to brachysm is indicated in the Acala variety. Even on the 
same plant, it often happens that some of the fruiting branches are normal while 
others are distinctly brachytic. Such differences of behavior have not been 
explained, but in view of the fact now recognized, that branching habits may be 
changed by growth disorders, it seems possible that some occurrences of brachysm 
may be connected with crazy-top or other growth disorders. Some features of 
crazy-top are similar to brachysm, or to abnormalities of branching that are to 
be associated with brachysm (PI. 4). The late-season fruiting branches of 
Pima cotton have the internodes very unequal, and the sockets of the pedicels 
defective, much as in cluster varieties of Upland cotton. (See PI. 3.) 
TOMOSIS, OR LEAF-CUT 
The chief feature in tomosis is the mutilation of the tissue of the leaf, with 
irregular perforations or marginal erosions, accompanied by more or less crump¬ 
ling or other distortion (PI. 5). The mutilations result from the death of por¬ 
tions of the leaf-tissue at early stages of growth. The dead areas are more fre¬ 
quent along the folds midway between the principal veins or along the margins, 
but may appear in any part of the leaf, and often with partial healing or regenera- 
