lo March, 1909.] The Stinking Smut of Wheat. 173 



6. Why is there more hunt from the same seed in one -paddock than 

 another 1 ■ 



There may be various reasons for this. The land may be fallowed in 

 the one case and not in the other. It may also be more moist in one 

 paddock and thus favour the germination of the spores at seeding time. 

 Actually wet soil would be inimical to germination. Whatever delays the 

 first growth of the wheat plant will be favorable to the increase of bunt. 



7. Does the date of seeding inf.uence the amount of hunt in the cropl 

 Different conditions at seeding time are likely to affect the result, 



but I have no definite experiments with regard to bunt which show it. I 

 carried out an experiment with flag smut which shows that the date of 

 .sowing has a verv decided influence. The seed was purpo.sely sown on 

 24th April and i6th July, or nearly three months between, on land that 

 had borne a crop badly affected with flag smut the previous season. The 

 first was sov/n when the ground was dry, but there seems to have been no 

 germination until the rain came, which germinated both the seed and the 

 smut, for there were up to 14 per cent, of diseased plants. The later sown 

 was about a month after the rain and the ground was in excellent order, 

 but the spores had evidently germinated and perished in the interval, for 

 there was only about i per cent, affected. 



It does not necessarily follow that this would apply to bunt, but the 

 weather and soil conditions enter so much into the result, that a dry or a 

 v;et seed bed at the time of sow-ing, or a spell of warmth or of frost at 

 the time of germination, is bound to make a difference. 



8. Why are some varieties more liable to hunt than other si 



As afterwards more fully discussed, this may be due to the fact that 

 the least liable variety germinates so rapidly that the smut plant is unable 

 to reach the growing point of the wheat and so dies, or there may be 

 something in the tissue of the variety unsuitable to the growth of the fungus 

 and so the variety is said to have the hereditary or inherent quality of bunt 

 resistance ! 



9. When all the grains are equally inoculated with sfores, why are 

 iome plants hunted and others not? 



It is quite a common occurrence for inoculated .seed to be sown under 

 similar conditions and yet a number of the plants escape infection. It is 

 not easy to answer the question, but a few considerations may help in 

 this direction. First of all, the young seedling must be at the right stage 

 of growth in order that the germ tube of the fungus may penetrate and 

 this period is of a very short duration. Next, the germ-tube must grow 

 and reach the growing point, or it would not be able to develop and pro- 

 duce the disease. But the main reason for some plants being attacked and 

 others not, lies in the fact that there are certain substances known as 

 chemotactic substances in the plant which favour the entrance of the germ- 

 tube of the fungus and its development inside. There are also substances 

 which actually repel the germ-tubes and it is the presence or absence of 

 these which determines whether an individual plant will be attacked or 

 escape. The seed from plants, however, which escaped infection in one 

 season have been sown the next and found to succumb. 



10. Why are some plants partially bunted — o)ily some of the ears being 

 affected and not all ? 



It often happens that only the secondary or late ears are affected, the 

 others being clean, and this might arise from the fungus filaments at the 

 base of the plant only reaching the growing point of the slow and late 

 developing plants, while the others escaped. In other cases where the fully 



