154 DISEASES OF CULTIVATED PLANTS 



Readily recognised by the needle-shaped appendages 

 springing from a large bulbous or swollen base. 



Hazel leaf mildew. During certain seasons there is quite 

 an epidemic of mildew on hazel leaves, which become more 

 or less completely covered on the under surface with a 

 delicate white mildew called Phyllactinia suffulta (Sacc.) 

 When this happens the leaves fall early in the season. I 

 once saw the hazel undergrowth of an extensive wood in 

 Yorkshire almost completely defoliated in July, due to an 

 attack of this fungus. I have also seen the fungus growing 

 on the young green nuts. Curiously enough although peri- 

 thecia or winter fruit are usually produced in abundance, 

 the disease may not appear again for years after a severe 

 attack. The fungus also attacks the foliage of many other 

 trees and shrubs. 



Perithecia scattered, hemispherical then depressed, com- 

 paratively large; asci 4-20, ovate, shortly pedicellate, 2, 

 rarely 3-4-spored; spores elliptical, size variable, 40-52 

 X 22-25 f 1 - 



I am not aware that any attempt has been made to com- 

 bat this disease, which appears to do but little injury to 

 cultivated plants. In all probability potassium sulphide 

 solution would answer, as in the case of allied pests. 



UNCINULA (LEV.) 



Perithecia with simple, rarely forked appendages, curled at 

 the tip. Asci several, 2-8-spored. 



Distinguished by the simple appendages being curled at 

 the tip. 



Powdery mildew of the vine. This destructive disease 

 of the vine was first detected in Europe in a vinery at 

 Margate, and as the conidial form of the fungus was alone 

 met with it was named Oidiitm Tuckeri by Berkeley. This 

 was in the year 1845, and within ten years it had spread 

 throughout the entire grape-producing countries in Europe, 

 Syria, Asia Minor and Algeria. The wholesale destruction 

 caused by this parasite proved ruinous to numerous culti- 

 vators, and led to the abolition of many vineyards in 

 different countries. For many years the conidial condition 

 was alone found in Europe, in fact it was not until 1892 



