28 PLANT DISEASES AND FUNGI. 



to no remedy for everything which shall be " worth a guinea per 

 box." Morison's pills are not yet invented which shall cure apple 

 scab, potato rot, or vine mildew. Empirics may arise, but empiricism 

 will effect no cure, except by accident. As there is no royal road to 

 knowledge in general, so there is no royal road to knowledge in this 

 particular instance, and no universal cure. It must be borne in 

 mind that there are at least two classes of fungoid diseases, viz., 

 those which are epiphytal, growing upon the plant from the outside, 

 and those which are endophytal, or developed from within the tissues 

 of the affected plant. Necessarily the means adopted for the cure 

 must have regard, first of all, to the one of the two classes to which 

 the fungus belongs. The epiphytal kinds are represented by our 

 ordinary vine mildew, by the hop mildew, by the mildew of peas, 

 by all those in which a web-like mycelium of delicate threads spreads 

 over the surface of the leaves, chokes up the pores, prevents the 

 iagress or egress of air, and suffocates the plant. In such diseases 

 the destruction of the fungus must be attempted in such a manner as 

 not to injure the host plant. This may be done by the application 

 of fungicides, and especially by the application of sulphur. It was 

 the discovery of this remedy which greatly mitigated the disease in 

 the hop and vine mildew, and is known to be the most beneficial in 

 any case of similar infection, but it is useless when applied to fungi 

 of the other class, which are endophytal, and must be treated in a 

 different manner. Another remarkable analogy here is presented in 

 the treatmeut of plants and animals. A short treatise by Dr. Valen- 

 tine Knaggs on " The Cure of Diphtheria by the Frequent Administra- 

 tion of Small Doses of Sulphur," affords this analogy. He says : 

 '' More than five years ago my father employed sulphur with magical 

 effect in a case which was at that time regarded as desperate. The 

 severity of the symptoms were hourly increasing under carbolic and 

 other applications ; but by the sulphur treatment, employed in the 

 manner I here advocate, the patient made a rapid recovery. Since 

 that time both my father and I have treated similarly seventy-two 

 cases, in all of which diphtheritic deposit was unmistakably and mark- 

 edly present. Though many of them were of a severe character, 

 some even with laryngeal complication, and accompanied by lividity 

 of skin, yet in not a single instance has a fatal termination occurred, 

 and in remarkably few of them have any of the ill effects which are 

 so apt to follow this complaint, even in the mildest and most transient 

 forms, resulted." Further on, and incidentally, he says: "Sulphur 



