ONION SMUT FUNGUS. 103 



losunc;." On the other hand, he found that TiUclia Trilici would not 

 gonnuiate at all in nutritive solution, but could be germinated easih' in 

 water. 



His experinieiits with nutritive solutions led Brefeld to believe that smut 

 spores in the soil are brought to germination and further development 

 through the influence of manure which has been used to fertilize the soil. 

 On this theory he explains the common observation of German farmers 

 that cereal smuts are more destructive on freshly manured fields. 



Host Stimulus. — One might expect that some stimulus from the host 

 plant would be necessary for germination, and consequently that a decoc- 

 tion from the host, or the presence of bits of it in the germinative medium, 

 would be necessary for starting germination. Although such host decoc- 

 tions have been successfully used, we find in the literature no instance in 

 which the}'^ furnished the only conditions under which the spores would 

 germinate. There seems, then, to be no evidence to indicate that a smut 

 spore must be in close proximity to, or in actual contact with, its host 

 before it T\ill germinate. 



Period of Rest. — But, even with the aid of nutritive solutions, and all 

 other conditions which have been tried, there is a considerable number of 

 species, the spores of which cannot be brought to germination immediately 

 after maturity. For these species, a period of "rest'" is necessary during 

 which the}'' must be exposed to certain natural conditions which operate 

 in some way to bring them into the proper condition for germination. For 

 our knowledge of this phase of the problem we are indebted, above all, 

 to Brefeld, and we cannot present it better than by quoting from his sum- 

 mary of it ( (4), page 128) : ^ - 



Only a part of these forms germinate at once even in nutrient solution, more 

 rarely in water; many will not germinate at all, but must be made capable of 

 germination by special methods. . . . The spores of many species are so adapted 

 in their time of germination that they do not proceed at once, but only after passing 

 through a shorter or longer resting period. In cases of this kind one has only to 

 wait until after the expiration of the resting period in order to bring them to ger- 

 mination. But one would often wait long and in vain, if he only kept the spores 

 dry in the house. Under these circumstances, the external influences are not 

 brought to bear, which operate in nature during the period of rest, and which must 

 operate in order to bring about those changes on which the initiation of germination 

 depends. For the most part, when simply kept dry the spores die without ger- 

 minating, except in a few cases, as, for example, the corn smut, . . . but even 

 here germination is always incomplete. It is necessary to obtain the conditions 

 which in nature operate on the spores and influence them to germinate, if one 

 wishes to succeed in observing germination. The simplest method would be to 

 expose the spores in nature or leave them in their natural habitat and observe 

 from time to time whether germination has begun. But in most cases it is entirely 

 impossible in this way to get and keep the material pure. 



He then describes in detail his method of keeping the material in steri- 

 lized damp sand in pots in a cool cellar. Then he continues: — 



' Translated by P. J. Anderson. 



