AND COLLEGE, PUSA, FOR 1915-16 47 



established that minute portions of infected plants were 

 only infectious when they contained On them individuals 

 of this species. During these experiments it was found 

 that definite symptoms may be induced in healthy seedlings 

 w r ithin a week when a moderate number of worms is used 

 for inoculation. A minute strip of plant carrying, say, 20 

 worms can be relied on to produce the disease in covered 

 seedlings, while a similar strip from the same plant and 

 part but without worms, is harmless. About a hundred 

 successful inoculations have now been carried out under 

 conditions which leave no room for doubt that the actual 

 parasite is this worm — perhaps the first case in which an 

 ectoparasitic eelworm has been found causing serious 

 injury to plants. Other points determined are that the 

 worm is not strictly aquatic, as it perishes in some weeks 

 if wholly immersed in water. Kept dry it lives longer, as 

 it has the faculty of coiling itself up into a twisted mass, 

 which resists moderate desiccation for at least some months. 

 It appears to be unable to grow much or moult unless sup- 

 plied with its usual living food and hitherto has not been 

 found to grow or feed on anything else than living paddy 

 plants. On paddy it is limited to parts where the outer 

 walls of the epidermal cells are unthickened, and in young 

 plants penetrates the bud to reach the young leaves near 

 the growing point as soon as possible. This position is 

 reached not by burrowing through the tissues but entirely 

 by passing between the folds of the bud. Several experi- 

 ments were carried out to test the ability of the worm to 

 remain alive in soil, and the results indicate that it cannot 

 survive during the interval between successive crops in this 

 manner. 



All the work hitherto carried out confirms the conclu- 

 sion previously arrived at that the parasite is normally 

 perpetuated by means of the stubble, which it is the prac- 

 tice m the infected area to leave on the fields after harvest. 

 The problem of dealing with the disease therefore resolves 

 itself into ascertaining the best way of removing or des- 

 troying this stubble. This can be done thoroughly by 



