INSTITUTE, PUSA, FOR 1916-17 65 



was the result of a natural infection from two neighbour- 

 ing trees which had since died. In fact it is most probable 

 that this tree was already infected in the lower roots when 

 the inoculations were made in June, 1916, but that the 

 disease had not at that time spread sufficiently near the 

 surface of the soil to be visible or produced sufficiently 

 marked external symptoms to enable the tree to be distin- 

 guished from its apparently healthy neighbours. This 

 case serves to call attention to a great difficulty in the work 

 at Rajabhatkhawa, namely, the impossibility of knowing 

 whether a particular tree is or is not infected with the 

 disease. The final stages of the disease are easily identi- 

 fied, the defoliation and death of the tree being accompanied 

 by the production of a large fructification and the presence 

 of " partridge wood " in the whole of the external tissues of 

 stem and root in the region of the ground level. A little 

 earlier than this however the tree appears quite healthy, 

 and the diseased tissues can only be found at a point about 

 1 foot below the ground level, or perhaps diseased tissues 

 may only be discovered by going down to a depth of 6 — 8 

 feet. It is therefore impossible to say that a tree is free 

 from infection until the bulk of the roots have been laid 

 bare, after which it is hardly a fair subject for inoculation 

 experiments. This objection does not however apply to the 

 infections carried out in collaboration with the Forest 

 Botanist at Dehra Dun and it is hoped that these may yield 

 more decisive results; arrangements have been made to 

 examine them in September, 1917. 



It is worth noting here that in diseases of large trees 

 caused by Basidiomycetous fungi, the parasitism of the 

 causal fungus has not invariably been established by the 

 method of direct inoculation, the constant association of 

 the fructification of the fungus with the symptoms of the 

 disease and the presence of the mycelium in the tissues 

 being, in some cases, the only direct evidence of the parasi- 

 tism of a particular species. From this point of view some 

 interesting information and figures should in a few years 

 be obtainable from the " fungus observation areas " in the 



