Parasitism and Immunity. 55 



It will be seen from the above that T. levis is generally the most virulent ; 

 but iu the case of Genoa it was the reverse, T. tritici being considerably 

 more so. 



It has been pointed out by Harwood^ that there is an evident difference 

 between the w^heat attacked by T. tritici and T. levis. With the former the 

 stalks are as tall as those with healthy grain, while with the latter they are 

 shorter, and this difference is so striking that in some parts of Michigan they 

 are spoken of respectively as " high " smut and " low " smut. This would 

 seem to indicate that the one smut interferes with the growth of the wheat 

 plant much more than the other, but in our plots there was no perceptible 

 difference between the two. 



Kapidity of Germination and Smut Liability. 



It is well known that wheats vary considerably in their susceptibiUty to- 

 wards stinking smut, and that while some varieties are very liable to it, such as 

 Allora Spring, others are very resistant, such as Minnesota Blue Stem and 

 Medeah. Dr. AppeP of Berlin observed that a square-head wheat originally 

 grown in Ohio was susceptible in a very slight degree, and that it germinated 

 so quickly that it very soon passed the stage when it was capable of infection 

 by the germinating spores of the smut. It is believed that this rapid germ- 

 ination is associated with a lessened liability to smut, as othei varieties with 

 similar properties germinated quickly, but we have yet to ascertain whether 

 this is a principle of general application as regards the wheats grow^n in 

 Australia. Kirchner^ has investigated a large number of spring and winter 

 varieties to see if any relation exists between their susceptibility to bunt 

 and their germinative energy. He did not find that a low germinative energy 

 was associated with susceptibility, nor that a high germinative energy was 

 an unfailing character for determining bunt resistance. But Hiltner\ who 

 found that rapid germination is characteristic of wheats that withstand the 

 smut, points out, with reference to Kirchner's results, that a good deal 

 depends on the mode in which the germination is conducted. The author, 

 with his specially constructed germinating apparatus, found that oats from 

 one district germinated 90 per cent, in five days, and from another district 

 in the same time 35 per cent. ; but when tested in the usual way, between 

 moist blotting paper, there was no distinction showai in the germinative 

 energy of the two. 



Any tests made in connexion with the relative rapidity of germination are 

 worthy of being recorded, and the following refers to four varieties. I 

 received a sample of Ohio wheat and germinated it along with Florence and 

 Genoa, which are comparatively resistant to bunt, as well as Warden, which 

 has proved itself to be very susceptible. The seed was sown at an even 

 depth in shallow pans in a sandy loam, and well watered. As the weather 

 was very warm at the time, germination was rapid, and in four days two 

 seedlings of Ohio were above ground and one of Genoa. In six days the 

 totals were — Ohio 6, Genoa 4, Florence 16, Warden 14: ; and in eight days — 

 Ohio 20, Genoa 16, Florence 18, Warden 18. The photographs in the frontis- 

 piece show well the relative rapidity of germination and strength of the 

 seedlings of each variety, and it W\\\ be noted that the Ohio was much the 

 most vigorous, the Genoa and Florence being about equal, and the Warden 

 much slower and weaker. These differences in vigour tended to disappear 

 with age, till on the fifteenth day there was no perceptible difference between 

 the Ohio, Florence, and Genoa, though the Warden was scarcely so forward 

 (Frontispiece). 



Escape of Injection hi/ individual Plants. — It is quite a common observation 

 that when the individual plants of a variety of wheat are all dusted equally 



