ONION SMUT FUNGUS. 105 



however, the smutted onions were stored until January, then mixed with 

 wet earth and frozen for a week or more, the spores germinated when 

 kept moist in a warm room. They also germinated in an onion decoction. 

 He also made pure cultures in onion decoction horn fresh spores and from 

 sporiferoils hypha?, but does not mention germination in this respect. 

 Such, in full, is the extent of our present knowledge of the necessary condi- 

 tions. The purpose of the wTiter's experiments was twofold: (1) to dupli- 

 cate Thaxter's work and (2) to extend the inquiry in order to determine 

 more exactly many points which Thaxter either did not touch or treated 

 insufficiently. The experiments are summarized below. 



Fresh Spores in Water. — Spores from a fresh but mature lesion were 

 scattered in a drop of w^ater on a slide kept in a Petri dish with water in 

 the bottom of the dish to prevent evaporation of the drop on the shde. 

 This common and familiar method was used in all the experiments where 

 water or a water solution was tested. Both distilled water and tap water 

 were tried. The spores were examined daily for aver two weeks, but no 

 indication of germination was observed. The experiment was repeated 

 many times, and the temperature and light relations were A'^aried in differ- 

 ent sets, but always without result. Spores taken from lesions which had 

 been kept dry for a. year in the laborator}'- gave no better results. 



Fresh Spores in Soil Water. — A soil extract was made by filling a 

 beaker wdth good onion soil (taken from a field where smut was abundant) , 

 adding water until the soil was saturated and the water was 1 cm. deep on 

 top of it, stirring thoroughly several times and filtering off after several 

 days. Results were the same as with tap and distilled water. 



Influence of the Germinating Onion Seed. — These tests were in every 

 way like those described above with water, except that a few germinating 

 onion seeds were placed in each drop in addition to the spores. With one 

 exception, in these tests the spores failed to germinate. On one slide a 

 very few spores germinated in close proximity to the young cotjdedon. 



Fresh Spores in Soil Decoction.- — A mixture of soil and water w^as 

 cooked for one hour on two successive days in the autoclave at 14 pounds' 

 pressure, filtered, tubed and sterilized. It was hoped that in this way 

 more of the soil substances would be brought into solution, and that they 

 might bring about germination. But, just as in the case of the soil extract, 

 so with this more concentrated soil decoction, there was no germination. 



Fresh Spores in Dung Decoction. — This decoction was prepared just as 

 Brefeld prepared his "nahrlosung" which he used so successfully on the 

 spores of a large number of species. Fresh spores failed to germinate in 

 it. In these experiments the solution was concentrated. It is possible 

 that if it had been more diluted the results might have been different. 



Fresh Spores in Onion Decoction. — This decoction was prepared by 

 boiling a shced onion in a pint of water for one hour. It was then filtered, 

 tubed and sterilized one-half hour at 15 pounds' pressure. This appears 

 to furnish an excellent medium for the growth of bacteria and fungi, and 

 in working with it every possible precaution must be used to prevent con- 

 tamination. These organisms grow so fast that they soon obUterate the 



