— ge- 

 ls vastly greater ; and just in such proportion must be 

 the injurious effects of a vitiated atmosphere upon it. 

 The presence of insects in a degenerated tissue is not 

 prima facie evidence of their being the cause of the 

 degeneration and it is to be regreted that Mr R. 

 Thompson, the Deputy Conservator of Forests of 

 India didn't say more to this effect in this Report on 

 the forests of Mauritius. 



A neglected gangrene will become full of maggots, 

 but they were not the inciting cause. The same may 

 be said of fungi, particularly of such as the yeast 

 plant, which develop whenever chemical changes inci- 

 dent to cremacausis or decay present themselves in 

 any organic matter or living organization. 



The mildew on grape vines is well known to be 

 caused by atmospheric influences ; the mildew or fungi 

 is not a cause, but only a secondary effect. Sulphur, 

 or rather the sulphurous acid gas which it contains, 

 is a specific cure for it, generally supposed to directly 

 destroy the fungus ; but it more probably destroys it 

 by the gas being taken up by the leaves of the plant, 

 thus absorbed into its sap, and so restoring the leaves 

 to a healthy state, which in such a state do not afford 

 the food necessary to the life of the fungus, and it 

 therefore perishes. All these gangrenous diseases of 

 plants are contagious if any portion of the diseased 

 plant is introduced into a healthy one. If a knife 

 used in pruning such a diseased plant be afterwards 

 used in pruning a healthy one without proper cleaning 



