On native plants of Gossypium peruvianum and G. iritifolium affected leaves show an upward marginal curl and are thick and brittle; thickenings on the underside of the veins strongly resemble those described by Raciborski for the Kroepoek disease of tobacco. A yellow and green mosaic mottling with the thin and thick areas characteristic of virus diseases also occurs, especially on G. hirsutum, but may not be identical with the above outgrowth type. Recovery does not occur but, even though infection by budding has been demonstrated, infection by juice or by Jassid insects has failed. This Leaf Curl is especially prevalent in spring. Several indigenous Malvaceae also show symptoms. It occurs throughout Nigeria and perhaps also in the Anglo-Egyptian Sudan, and is probably a virus disease. A functional disorder (Leaf Roll) discovered in Nigeria, more prevalent on American than on native cottons, is characterized by a downward marginal leaf roll or crimp and a glazed undersurface, with cracking and fenestration of the leaf in severe cases. On native plants it resembles Curly Leaf of Sea Island cotton. The symptoms are apparently caused by collapse of the lower epidermal leaf cells. Assimilation of affected leaves is greatly reduced, while translocation exceeds assimilation The disorder develops in rainy weather, but plants in the shade are less affected; recovery occurs as aridity increases. The disorder was artificially induced by heavy watering in unshaded but not in shaded plants. The predisposing environmental factor is excessive soil humidity, rather than indirect effects such as leaching of solutes and root asphyxiation.