542 



DISEASES OF CULTIVATED PLANTS 



that is surrounded by several other birches, many of which 

 remain perfectly free from disease, while others show a few 

 scattered tufts only of infected buds. 



Eriophyes nervisequus (Can.) forms minutely velvety patches, 

 consisting of crowded, more or less irregularly club-shaped 

 hairs, on the under surface of living beech leaves. These 

 patches are sometimes of a beautiful crimson colour, more 

 frequently reddish brown, and sometimes greenish. Some- 



FiG. 164. Eriophyes rudis, causing arrest and galling of buds of 

 Betula alba. 



times narrow lines of these hairs follow the larger veins on the 

 upper surface of the leaf. These velvety islands are by no 

 means uncommon on the upper or under surface of living 

 leaves belonging to various kinds of plants, and were at one 

 time considered as fungi, and included under the genus 

 Erineum (Pers.). 



Eriophyes kernen (Nal.) is recorded as being the cause of 

 galled gentian flowers (Gentiana campestris, L.) in Scotland. 

 The flowers remain closed but much swollen and distorted. 



