Report on the Diseases of Wheat. 



21 



of an inch in diameter. When full grown, the vibrio acquires a 

 monstrous size compared with one of the multitude which com- 

 poses the cottony mass in the blighted grains, becoming a quarter 

 of an inch long, and the -^^J of an inch in diameter. I am not aware 

 whether any precise estimate of the numbers actually found in a 

 single grain has ever been made, but a slight calculation will 

 show us that not less than fifty thousand of the young might be 

 packed in a moderately sized grain of wheat. Mr. Bauer seems 

 to think that more than one generation are produced in the course 

 of a season. The most curious circumstance which observers 

 have noticed in the economy of this animal, and which I have had 

 an opportunity of fully verifying, is the wonderful property it 

 possesses of retaining its vitality under circumstances in w^hich we 

 should have supposed it impossible that it could have lived. If a 

 mass of them is suffered to become so perfectly dry that the 

 slight touch of a hair might reduce them to powder, and they 

 are again moistened in a drop of water, they will speedily revive, 

 and become as active as before. They may thus be dried and 

 revived many times before they are killed. Mr. Bauer states the 

 limit to such revivals to lie between six and seven years. I 

 happened to possess an ear of wheat infected with this disease, 

 which had been sent me (I think) at least six years ago, but 

 which I had not minutely examined before; and upon soaking 

 some of the blighted grains in water for a few hours, the animal- 

 cules revived, and were quite as active as those I had found in 

 the first fresh grains which I had been examining only two days 

 previously. If the eggs are once dried^, or even the young ani- 

 malcules themselves before they have attained a certain size, they 

 will not revive on being moistened. It does not appear that the 

 vibrio naturally attacks any other corn than wheat ; at least, it has 

 not been observed to do so. But barley, rye, and oats may 

 become infected by sowing them in the same hole with the grains 

 of wheat which are filled with the vibrio. The experiment, how- 

 ever, succeeds with difficulty, and only to a small extent. 



Section XII.- — On the prevention of the Ear-Cockle. 



When the infected grains are thrown into water, they float 

 for a short time, but on becoming saturated with moisture, they 

 sink ; so that merely immersing the seed-sample in w^ater would 

 hardly suffice as a method for getting rid of the bad grains. I 

 have observed that scalding water kills the vibrio ; and this may 

 suggest the possibility of exposing infected samples to a tempera- 

 ture that might be sufficiently high to kill these animalcules, with- 

 out being so hot as to destroy the germinating powers of the corn. 

 Perhaps the suggestion already thrown out, to grow seed-wheat 

 apart from the general crop, may be here repeated. 



