6 hitrodnciion. 



produced by superabundant manure foreign to the nature of the pknt. At 

 one or at several places of the inner surface of the affected cells, small deposits 

 of mucus are formed from which filiform ramified bodies proceed, which are 

 colourless and almost transparent, but contain a quantity of small molecules 

 consisting of a somewhat more solid substance. These mucous filaments, in 

 the interior of the cells, soon present constrictions at various places, first 

 generally at the apices of the small lateral branches ; and these constricted 

 ends take an ellipsoidal and lastly, a spherical form, become of a yellow colom-, 

 and change into those minute brown vesicles of which the smut consists. The 

 destruction of the cellular walls by dissolution commences with the aggrega- 

 tion of these smut vesicles in the diseased cells, and then these vesicles are 

 found in great masses lying close together, filling entirely the diseased organ, 

 and frequently without leaving a trace of the original intervening cellular 

 wall.'" It is still deeply rooted in the minds of many farmers that the smut 

 spores are simply an exudation of the sap of the plant, blackened by exposure 

 to the air, or that the fungus, if fungus it be, has arisen spontaneously from 

 the soil in some mysterious fashion. It is only when the spores are seen to 

 germinate, and when the infected grain produces smutted plants, while those 

 produced alongside free from spores are perfectly healthy, that the fungus is 

 realized to be a parasite, the presence of which is necessary for the production 

 of the disease. 



The next step in advance was by Tulasne\ in 1847, who investigated 

 methodically the germination of the spores in water, and proved that on ger- 

 mination they did not directly give rise to a mycelium, but to a short germinal 

 tube which produced minute reproductive bodies. He distinguished the 

 germinal tube as a promyceUum, and the reproductive bodies as sporidia,and 

 having a somewhat similar mode of germination to the teleutospores of the 

 rusts, he came to the conclusion that the rusts and the smuts were closely 

 allied. Next, Kuehn^, in 1858, carried out infection experiments with the 

 spores on various host-plants, and he found that the fully developed plants 

 were not capable of infection, but only when they were in the seedling stage. 

 The production of sporidia, as shown by Tulasne, and the mode of infection of 

 the host-plant as demonstrated by Kuehn, gave a simple explanation of the 

 development of the smut, and seemed to account completely for all the ob- 

 served phenomena. When one considers how intimately the smut fungus is 

 associated with its host, how it enters the young seedling and goes on growing 

 within the tissues of the apparently healthy plant, how it suddenly appears 

 in the ovary and replaces the floury contents of the grain with the black smutty 

 spores, it is not to be wondered at that it was regarded at one time as part 

 and parcel of the plant itself. 



The mode in which the spores are formed next engaged attention, and 

 De Bary\, as early as 1853, extended our knowledge in this direction. 

 Fischer von Waldheim^ also carried on his investigations into the germination 

 of the spores and the mode of their formation. But it was only when Brefeld 

 began his masterly and epoch-making researches into the germination of the 

 spores of the various smut fungi in nutrient solutions that the subject was 

 dealt with in a thorough and complete manner."]. This was in 1883, when the 

 first part of Die Brandinlze was published, and there he showed that it is only 

 by rigorously following exact scientific methods that the boundaries of know- 

 ledge can be enlarged. He found that the germination of the spore in water 

 was often uncertain, slow, and in some cases, such as Maize Smut, it was diffi- 

 cult to secure it at all. He therefore hit upon the happy expedient of germina- 

 ting the spores in nutritive solutions, such as a watery extract of manure, or 

 of such vegetable substances as are contained in the soil. In the fluid extracts 

 of such materials, not only did the spores germinate as in water, but even 



