THE FUNGI WHICH CAUSE PLANT DISEASE 397 



EricacejE. Cultural work and studies in infection are needed be- 

 fore species can be properly delimited.'' 



E. vaccinii (Fcl.) Wor. occurs on Vaccinium vitis idaea, forming 

 large blisters on the leaves, 

 rarely on petioles and stems, 

 discoloration red or purple. 

 The fungus appears as a 

 white bloom on the under 

 surface of the leaf; spores 

 narrowly fusiform, 5-8 x 

 1-2 n. 



Richards ^ who studied 

 E. vaccinii and E. an- 

 dromedse from inoculations 

 concludes: 



"Aside from the form of 

 the distortion, E. vaccinii 

 and E. andromedae cannot 

 well be distinguished. The 

 former can produce the same 

 form of distortion on both 

 Gaylussacia and Andromeda 

 and the latter has been made 

 to produce a similar growth 

 on Andromeda. Micro- 

 scopically these forms do 

 not differ. The natural 

 conclusion is that these two 

 species of Exobasidium are 

 one and the same and the form producing large bag-like dis- 

 tortions on Andromeda should be considered a form of E. vac- 

 cinii." 



E. ozycocci Rost causes greater hypertrophy than E. vac- 

 cinii, distorting young twigs and leaves; spores 14-17 x 30 n; 

 smaller conidia often present. The myceliiun infests the leaves 

 and stems of the cranberry.^" Morphologically the species agrees 

 closely with E. vaccinii. Infection experiments are needed. 



E. vezans Mas *^ causes a serious disease on tea. E. andromedae 



Fig. 284. — ^Exobasidium andromedae on An- 

 dromeda, showing host cells, mycelium, 

 basidia and spores. After Richards. 



