Acromania, or "crazy-top," a Growth Disorder of Cotton

Some of the diseases of cotton are manifested by abnormal growth of the plants, without localized injuries like those associated with parasitic fungi or bacteria. A remarkable feature of growth disorders is that the plant characters and habits of growth may be changed suddenly, the normal characters being replaced by abnormalities of many kinds and degrees. The changes of characters often are so complete that the abnormal growth would not be recognized as belonging to the same variety as the early growth of the same plant, or even to the same species, if the connection were not known. To appreciate the extent of the abnormalities, it is necessary to be familiar with the normal characters and development of the plants, as in the study of breeding and adaptation of varieties. Similar disorders affect other plants, and some of them are known as mosaic diseases, because the leaves are discolored in irregular patchwork areas of light and dark green. But in crazy-top the growth is abnormal in other ways, without discoloration of the leaves. Some of the disorders are temporary, with a later return to normal growth, while other disorders are permanent so that the abnormalities continue to appear in all of the new growth that takes place. When the changes of characters are permanent the growth disorders appear somewhat analogous to "bud mutations." Since the symptoms of crazy-top are aggravated by stress conditions, it might be expected that the cause would be found in some peculiarity of the environment. The presence of harmful substances in the soil is easy to assume and difficult to disprove, but with crazy-top there is no indication that any particular type or condition of soil is associated. The disease occurs under a wide range of cultural conditions, and appears sporadically in scattered individuals, as well as in more compact groups of plants, or in large areas. The mode of occurrence of crazy-top is consistent with the possibility of an infection distributed by insects. It is known that several of the mosaic diseases of other plants are carried by insects, and that some of the diseases are very infectious, so that only slight surface contacts are necessary to spread the "virus." The underlying cause of mosaic diseases is still obscure, even with those that have been studied most carefully, as in sugar-cane, sugar-beets, tobacco, and potatoes. Some pathologists credit the idea of very minute Protozoa, smaller than bacteria, beyond the limit of microscopic vision, as indicated by the passage of contagious "virus" of mosaic disorders through filters that are impermeable to bacteria. Other investigators have sought for causes of such diseases in organic poisons, or in the reactions of organic ferments or "enzymes." The causes, no doubt, are different for the disorders that are not permanent nor infectious, though one of the temporary disorders of cotton is due to plant lice. Another may be a physical injury or traumatism, primarily affecting the oil-