DISEASES OF CULTIVATED PLANTS 335 
heads will not germinate. It was also found in continuous wheat 
land as much as 6 percent of the young wheat plants were destroyed 
in the fall by this same parasite which appears to survive in the soil 
under continuous ‘wheat growing as well as to be propagated in the 
seed grain. 
Fig. 15. This shows results from germinating ten wheat kernels in 
Petridish containing agar. Both the agar and the kernels were sterilized. 
After five days it was found that five kernels had produced healthy plantlets, 
and four kernels had germinated but were attacked by the scab fungus, 
Fusarium, and two by anotherfungus. One kernel in the center did not 
grow and gave only growth of the scab fungus, Fusarzum, (From Bul. 203). 
HOW TO EXAMINE SEEDS FOR INFECTION 
Recently good success has been obtained in the laboratory of this 
Department in determining the presence of certain seed infesting 
fungi in seed wheat, oats, rye, etc. In regard tothe matter of 
adhering spores this is accomplished by making washings of the 
seed in distilled water and separating the spores from the washings 
by means ofa physician’s centrifuge. (Fig. 14). The spores and 
similar particles washed from the seeds are thus collected in the 
bottom of the tubes of the centrifuge and may be identified by 
microscopic examination. (Fig. 16). 
