E. J. BUTLER 19 



of the stem just above the upper nodes, and the leaf sheath, must be added 

 the young leaf blades inrolled towards the centre of the bud above the growing 

 point. When seedling plants are inoculated, the latter is the point where the 

 worms collect. They enter between the folds of the bud (never actually 

 penetrating the tissues) and work their way round these towards the inner 

 layers. Seedlings of about a fortnight from germination and six days after 

 inoculation have been found to contain very many worms under the outer, 

 still rolled, green leaf, and within the succeeding leaves and sheaths right in 

 almost to the growing point. Naturally-infected aman plants have also been_ 

 found in August, when about half grown, to contain pure cultures of enormous 

 numbers of Tylenchus angustus in the white central part of the bud. In this 

 case the plants were 2| to 3 feet high, and all the leaves were removed until 

 the central white bud, | to 2 inches long, was reached, when further dissection 

 became difficult. The last few leaves around the growing point are so tightly 

 rolled that they are not usually penetrated until loosened by the developing 

 ear. Prior to this, the growing point is not reached and the worm feeds chiefly 

 on the young leaves. Here it does not cause sufficient damage to kill the 

 plant or even to cause any very marked symptoms except chlorosis and some- 

 times stunting. As the leaves mature, the outer cell walls thicken as described 

 in the previous paper and feeding becomes impossible. Worms are scarcely 

 ever found on any but the very young leaf blades, and when found they are 

 probably only migrating, not feeding. It is not until the ear is forming and 

 the worms collect at its base and above the top nodes of the stem that the 

 strain becomes more than the plant can meet. It is quite possible to keep 

 even severely infected young plants growing, but often impossible to get them 

 to bear mature ears. 



Feeding is exclusively by sucking out the juices from the epidermal cells 

 of the infected parts. The spear which perforates the wall is only 9 or 10/a 

 long, and is unable to penetrate any but unthickened or slightly thickened cell 

 walls. Microtome sections of young infected leaf buds have not shown any 

 very definite signs of injury to the cell-contents where the worms were feeding. 

 There is no evidence of toxic action, so that the injury is presumably entirely 

 due to continued removal of the cell sap. In other parts, as around the stem 

 and base of the peduncle, the cells collapse and turn brown, but bacteria and 

 fungi so rapidly follow the injuries caused by the worm that it is hard to 

 separate their effects. The lower part of the last internode and the base of 

 the peduncle may be shrunken to little more than the thickness of a thread. 



Reproduction undoubtedly goes on vigorously on the plant during the 

 period from June to November. Eggs and larva; in all stages are found mingled 



