IOWA ACADEMY OF SCIENCES. 177 



Verrucaria fuscella (Fr.) On limestone. La Crosse, Wis., 

 January, 1895. Coll., L. H. Pammel. Quite as rarely collected 

 as the last. 



Verrucaria muralis (Ach. ) On limestone. Rooks county, Kan. , 

 March, 1893. Coll., E. Bartholomew. And La Crosse, Wis., 

 January, 1895. Coll., L. H. Pammel. 



Pyrenula punctiformis (Ach.) Naeg., var. Fallax Nyl. On 

 trees. Emma, Mo., July, 1898. Coll., C. H. Demetrio. 



Pyrenula thelena (Ach.) On trees. Emma, Mo., July, 1898. 

 Coll., C. H. Demetrio. 



POWDERY MILDEW OF THE APPLE. 



BY L. H. PAMMEL. 



There has been much discussion on the subject of powdery 

 mildew of the apple. It has been referred to several genera 

 but Sorauer* in his book on -'Plant Diseases" and Tubeuf f in his 

 work on "Plant Diseases " reports the PodopshcBra oxyacanthce 

 DC, as destructive to the apple, and makes the statement that 

 it is abundant upon the apple and pear in America. Frank^ 

 in the second edition of his work on "Plant Diseases" makes 

 a statement somewhat similar to that of Tubeuf. These state- 

 ments are undoubtedly based upon the work of Galloway, § who 

 paid some attention to the subject of a powdery mildew upon 

 the apple. Several American writers have briefly referred to 

 the occurrence of a mildew upon apples, among them, Fair- 

 child and Galloway, who made some experiments in treating 

 this disease. Professor Galloway, || in a paper on the common 

 mildew of the cherry, records the occurrence of this fungus 

 upon the apple, and it is also recorded here upon the quince 

 and wild crab. In a circular issued by Galloway,! mention is 

 made of this fungus under the name of Podosphcera oxyacanthce 

 and in a later paper** the fungus is again referred to under the 



« Pllanzen Krankhelten 330. 

 tPflanzen Krankhelten 193. 

 * Die Pllzp. Frank, d Pflanzen 259. 



§ Olrc. U. 8. Dept. of Agrl., Dlv. of Vegetable Pathology 8. 

 11 Rep. Dept. Agrl. 1888: 353. 



H U. 8. Dept. Agrl., Dlv. Veg. Path. 8. See also ZeitBCh t. Pflanzen 1 :97. 

 •*Jour. Myc. 6;U. 

 12 



