296 PLANT DISEASES 



blotches are often bordered by a dark, slightly raised line. 

 Diseased leaves are not at all blistered or swollen ; in fact, 

 the grey patches are thinner than the uninjured portion of 

 the leaf, owing to collapse of the tissues. 



Dr. Watt states that the disease commences for the 

 most part on one side of a bush, very often on the same 

 side of all the bushes over an affected plot — a circumstance 

 that may be taken as indicative of the germs having been 

 wind-conveyed. 



In addition to growing on the tea plant, Pestalozzia 

 guepini also occurs as a parasite on other species of 

 Camellia and on Rhododendron in India ; in Europe it is 

 not uncommon on cultivated camellias and rhododen- 

 drons. In the United States it also occurs on introduced 

 species of Camellia and Citrus, from whence it possibly 

 passed on to the native Magnolia. Finally, it is known to 

 occur on indigenous plants (Niphobolus) in New Zealand, 

 and on Alphitonia in Queensland. 



Preventive Means. — The remarks I offered in the 

 Kew Bulletin are repeated here. If the diseased leaves 

 were collected with the amount of care and intelligence 

 exercised in collecting sound leaves, and burned at once 

 after being collected, the disease would soon be stamped 

 out, as the mycelium of the fungus is not perennial in the 

 tea plant ; consequently infection and a recurrence of the 

 parasite depends entirely on inoculation by the numerous 

 conidia or reproductive bodies of the fungus present on 

 diseased leaves. Remembering the very different kinds of 

 plants on which the fungus is known to be parasitic, it is 

 very probable that it also occurs on wild plants growing in 

 the vicinity of the tea-gardens. If such proves to be the 

 case, all such plants should be removed if practicable, as 



