The Take-all Disease of Cereals and Grasses 23 



Type I, which is characterized by the radiate habit of the strands, occurs 

 only on the 0.2-per-cent dextrose agar. Type II, which is characterized 

 by the strands intermixing on the plate and forming ribbon-like strands 

 of parallel hyphae, occurs when the fungus grows on the following agar 

 media: potato, cornmeal, bean, oatmeal, prune, nutrient, Czapek, crushed 

 wheat (Kirby, 1922), and 2- and 5-per-cent dextrose. On crushed wheat 

 agar aerial growth is much more abundant than on any of the other media. 

 Zonation does not occur on potato agar with a pH of 5 to 6, but it does 

 occur and becomes increasingly pronounced as the pH value decreases or 

 increases. 



The writer has been able to develop perithecia in culture, both in petri 

 dishes containing crushed-wheat agar and on sterilized sweet clover and 

 wheat stems. Different monosporous isolations of the organism showed 

 a marked difference in their capacity to develop perithecia. Some of 

 these were greatly stimulated in then development of perithecia by being 

 grown in apposition with other monosporous cultures. From a consider- 

 able number of these isolations perithecia were not obtained except when 

 they were grown in this manner. However, this was not true of all the 

 cultures studied, since some of them were found to produce perithecia 

 without stimulus of a second strain. It was believed in the earlier part 

 of the work that the majority of the strains of the fungus exhibited a true 

 he terothallism (Kirby, 1923). Subsequently strains have been found 

 which are not identical in their cultural reactions with either of the 

 original plus or minus types. Further investigation will be necessary 

 to determine whether or not the strains of this fungus can be segregated 

 into definite sex types. 



The characteristic signs and symptoms of the disease have been pro- 

 duced by inoculations of pure cultures of the fungus into healthy plants. 

 In several series of inoculation experiments, the soil of 457 pots con- 

 taminated with pure cultures of the fungus at the time of planting were 

 variously sown with wheat, rye, barley, or other species of grasses. Within 

 four months after planting, characteristic symptoms and signs appeared 

 on plants in all the pots, while the plants in 212 pots planted under the 

 same conditions excepting that no inoculum was placed in them never 

 showed signs or symptoms of take-all. 



In a field which was known to be free of take-all, 64 rod-rows of winter 

 wheat of different varieties were inoculated in the fall of 1921 with pure 

 cultures of the fungus, and in every row the same characteristic signs 

 and symptoms of the disease were produced as have been found in all 

 infected fields observed in New York. In this test field, the same symp- 

 toms and signs appeared when 47 rod-rows of winter wheat were inoculated 

 in the fall of 1921 by placing diseased straw brought from other fields 

 with the seed at planting time. Further take-all symptoms and signs 

 appeared when 45 rod-rows of winter whea,t were inoculated with our« 



