28o DISEASES OF CROP-PLANTS 



Comparison of notes and specimens with those of Longfield 

 Smith in St. Croix shows that in that island the crimping of the 

 leaves is not developed to the same extent, but that the occur- 

 rence of small irregular holes, as mentioned above, is so abundant 

 as to make this the most prominent feature of the disease. The 

 symptoms on the flower-buds and the consequent effect on bearing 

 are the same. 



Nature of the Affection. 



Careful investigation has revealed no evidence of association 

 with any insect, fungus, or other organism. The manner of 

 occurrence does not suggest a parasitic origin and the affection 

 does not appear to be communicable. It has no connection with 

 seed of any particular origin and can occur in old or newly 

 imported strains. It must therefore be attributed to some 

 functional disturbance connected with external conditions. 



Conditions of Occurrence. 



It is the firm opinion of local observers that the appearance 

 of ciirly-leaf is connected with dull rainy weather, and it is 

 especially liable to occur in shaded and sheltered situations. In 

 St. Croix the disease is always associated with vigorous growth 

 in the first two months after planting and is especially prevalent 

 on the eastern side of the island where the soil is deep. Cotton 

 planted on new land is generally worst affected. The stunting of 

 plants through water-logging has been noticed to cause their 

 escape from the disease, and the outermost rows of affected 

 fields commonly remain normal. 



The affection is by no means regular in its occurrence in the 

 same district at the same time. It is usually generally distributed 

 through a field in which it occurs, but in other fields may be 

 absent or only slightly developed. 



Accounts agree that normal growth is always resumed when a 

 period of dry sunny weather ensues. 



Causation. 



The conclusion indicated is that the curly-leaf disease is 

 definitely connected with rapid growth brought about under 

 certain soil conditions, including depth and easy permeability, 

 when plants in the active vegetative stage receive an abundant 

 supply of water and the checks to growth ordinarily exercised by 

 sun and wind are removed by the prevalence of still cloudy 

 weather, the shading of the situation, or the crowding of the plants 

 themselves. 



Loggerhead. 

 In the same season (1914) that the curly-leaf affection was 

 most abundant in St. Kitts and Nevis, a second form of abnormal 



