1897.] PUBLIC DOCUMENT — :No. 33. 81 



method in the long run would ])e to apply heat as a remedy 

 for fungus and other pests in the soil. I have used a great 

 many pots of earth heated with steam up to ISO'' to 200''F., 

 with the most beneficial results, not only in the subsequent 

 growth of the plant, but also in destroying the troublesome 

 pests which infest the soil. The soil under glass could be 

 easily fitted up with a system of irrigating tile, which could 

 be used not only for purposes of irrigation, but also for forc- 

 ing steam through them and partially sterilizing the soil. I 

 have not as yet had an opportunity of treating this fungus 

 with heat, but I should suppose that, if the soil was heated 

 to 200*^ F., it would result in its death. 



Physiological Disorders. 



Wilt of Maple Leaves. 



Last May a number of maple leaves in a dry and crispy 

 condition were sent to this department from various parts of 

 the State, under the supposition that they were affected by 

 some form of fungus or insect life. Examination of the 

 leaves, however, by Mr. Eobert A. Cooley of the insectary, 

 showed that no form of either of these organisms could be 

 found. All of the leaves that were sent in were those of the 

 sugar maple (Acer saccharinum), although the same con- 

 dition was observed in a large number of different varieties 

 of Japanese maple growing on the college grounds. More- 

 over, they showed the wilt only on one side of the tree, 

 namely, the w^est, that being the direction of the prevailing 

 wind the day upon which they were afiected ; and this pecul- 

 iarity — so far as could be learned — was the same all over 

 the State. This phenomenon is especially interesting, as it 

 occurs on apparently healthy trees under certain exceedingly 

 unusual conditions, — conditions, too, which, lasting only a 

 few hours, are yet capable of giving rise to abnormalties of 

 function. We attribute the wilting of sugar-maple leaves, 

 which occurred quite generally throughout Massachusetts on 

 May 18, to an excessive transpiration or evaporation of water 

 from the leaves, at a time when the water supply of the roots 

 was extremely limited. This was brought about by a re- 

 markable combination of meteorological conditions favorable 



