ONION SMUT FUNGUS. 131 



spores. In tlie largor loaA'Os the oi)ening of the sorus may first occur on 

 the interior of the hollow leaves, thider moist conditions other funpi, 

 such as P\isarium, may cause the tissue to decay more rapidly, and thus 

 aid in the liberation of the spores. 



The first outward indication of disease in a j'oung seedling is a slight 

 curvature of the cotyledon accompanied by some enlargement of the 

 affected part. In the greenhouse I have found these s\^llptoms as early 

 as the tenth day after planting. Within another day or two, when an 

 affected seedling is held so that the light will shine through it, the lesions 

 may be located by the darker appearance. As soon as the spores are 

 mature the dark sorus can be seen through the tissue without holding it 

 up to the light. The length of time which elapses before it splits open 

 and permits the escape of spores varies greatly with the weather, age of 

 leaf, and other factors. 



VII. Summary. 



1. Spores as soon as mature germinate in the laboratory in onion 

 decoction, sugar solutions, onion decoction agar, soil agar, manure decoc- 

 tion agar and various agars containing sugar. 



2. The}' do not germinate in tap water, distilled water or soil water. 



3. The presence of the onion or any substance from the onion is not 

 necessar3^ 



4. Freezing does not increase or hasten germination, but when spores 

 are frozen in the ground they are not killed. 



5. Free access to air increases the percentage of germination. 



6. A period of rest in damp soil increases the percentage of germination, 

 but is not necessary. 



7. In the soil the spores do not all germinate at once, but become pro- 

 gressively prepared for germination. They do not wait until a host plant 

 starts to grow near them. 



8. Germination begins in three to six days after the spores are brought 

 under favorable conditions. 



9. A short hemispherical promycelium is first developed, and from this 

 a whorl of branches grows out. 



10. The branches grow as mycelium indefinitely without producing con- 

 idia (sporidia) . The older cells become devoid of their protoplasm progres- 

 sively. 



11. The germination process is very similar to the same process in 

 other species of Crocj^stis, being almost identical with that of Urocystis 

 Anemones. Of the investigated species of this genus, only U. FioZae pro- 

 duces sporidia. 



12. Urocystis cepidae lives and grows as a saprophyte indefinitely in the 

 soil, its gro-vvi;h being favored by manure. 



13. It may be grown in pure culture on a wide range of culture media, 

 and shows cultural peculiarities by which it may be distinguished from 

 other fungi. 



