ONION SMUT FUNGUS. 131 



spores. In the larger leaves the opening of the sorus may first occur on 

 the interior of the hollow leaves. Under moist conditions other fungi, 

 such as Fusarium, 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 young seedling is a slight 

 curvature of the cotyledon accompanied by some enlargement of the 

 affected part. In the greenhouse I have found these sjTnptonis as earh'- 

 as the tenth day after planting. Within another daj^ 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 ^Nith the weather, age of 

 leaf, and other factors. 



VII. SUMMAKY, 



1. Spores as soon as mature geniiinate in the laborator}- in onion 

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

 tion agar and various agars containing sugar. 



2. They do not germinate in tap water, distilled water or soil water. 



3. The presence of the onion or an}^ substance from the onion is not 

 necessary'. 



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 gemiination, 

 but is not necessar}'. 



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

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

 starts to grow near them. 



8. Germination begins in three to six daj's after the spores are brought 

 under favorable conditions. 



9. A short hemispherical promyceUum is first developed, and from tliis 

 a whorl of branches grows out. 



10. The branches grow as myceUum indefinitely \s-ithout 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 Crocystis, being almost identical with that of Urocystis 

 Ananmes. Of the investigated species of this genus, only V. UioZae pro- 

 duces sporidia. 



12. Urocystis cepxdae lives and grows as a saproph^-te indefinitely in the 

 soU, its growth being favored by manure. 



13. It may be gro"mi in pure culture on a wide range of culture media, 

 and shows cultural peculiarities by which it may be distinguished from 

 other fungi. 



