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itself in the wilting of the edges of the leaf which subsequently die, 

 thus producing a narrow whitish area of dead tissue and preventing 

 the leaf from further expansion. As the other part of the leaf 

 grows, while the whitish dead edge is restricted in this respect, it 

 results in the exterior surface of the leaf assuming a convex form 

 with a contorted margin. In other words, the leaf is curled up more 

 or less like a ball. Single plants now and then occur in a house 

 affected in this manner, while all the other plants may be normal 

 in this respect. Occasionally many plants will show only slight 

 symptoms of curling, which would be the case when the wilting and 

 dead areas occur after the leaves have practically reached their max- 

 imum size. There are various stages of this trouble ranging all the 

 way from a slight curling to pronounced types. These various stages 

 bear a relationship to the plasticity of the plant and its relative 

 development, together with the nature of the cause and the degree 

 of intensity with which the abnormal stimulus has been applied. 

 This wilting and dying of the margin of the leaf may evidentlv be 

 brought about in more than one way. In all instances that we 

 have observed the phenomenon is one connected with absorption and 

 transpiration or the taking on and giving oft of water. The most 

 frequent cause of this condition, however, is over manuring. 

 We have succeeded in producing plants where practically all the 

 leaves assumed the spherical form by growing them in an excess of 

 manure. If strong horse manure at the rate of two-thirds or three- 

 fourths is mixed with one-third or one-fourth soil, such results can 

 usually be obtained. Some of the worst cases we have seen were 

 where the soil had been liberally treated with horse manure with the 

 addition of a considerable quantity of hen manure. Over manuring, 

 however, is not the only cause, and cases have been observed bv lis 

 where it has occurred without an excess of manure in the soil. It 

 can be induced in various ways, and abnormal modifications in the 

 light, soil and moisture conditions under which plants are grown are 

 frequently responsible. Any cause which is likely to produce exces- 

 sive transpiration, such as lack of texture in the leaf, etc., or anything 

 which prevents root absorption, as the presence of a considerable 

 amount of nitrate, etc. in the soil, will succeed in producing a curl- 

 ing of the leaf when other necessar}' conditions are at hand. Care 

 should therefore be taken in not over manuring, also in the regula- 

 tion of those conditions which produce plants of inferior texture. 



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