S3 



According to the earlier hypotheses, infection ivas dependent on the direct products of 

 germination of the smut spores; therefore, so io speak, on these alone. It was assumed from 

 the z^'cakly genninating smut spores that they inoculated the germinating seedlings and 'that 

 from these inoculations smutted plants were produced in our grain fields. This theory, however 

 short and conz'cnient for the e.rplanation of smut infection, has been suppkmented by the proof 

 of an c.vtcnsivc distribution and propagation of the smut germs in saprophytic substrata outside 

 of the host plants. 0)ily by determining this has the way, in ivhich the germs of infection are 

 distributed, become clearly and certainly understood, as well as the natural infection and distri- 

 buhun of smut genus as observed uuiirrsally in nature. The biological section zvith the devel- 

 opment of smut fungi on saprophytic substrata outside the host plants, forms, according to our 

 present understanding, the complement of the section with development taking place in the host 

 plants. Both parts are nozv united in a harmonious whole and nothing can characteri::e this 

 harmonious union further and more sharply than the fact that, for instance, in the forms of\ 

 the genus Ustilago, at the time of parasitic life in the host plants, only chlamydospore fruit forms, 

 the typical smut spores, mature and that during the period of saprophytic nutrition only conidia 

 fruit forms appear. For this strict alternation in the maturing of the fruit forms which takes 

 place here, not, as in the case of the Uredineae, on two different hosts, but after saprophytic and 

 parasitic nutrition, 7^<e can for the present find no other e.rplanation than the influence exer- 

 cised on the development of our plants, at one time by the liz'ing substrata, the next time 

 by the dead substrata. How would it be possible, according to the earlier conceptions and the 

 earlier knowledge which had not led even so far as to the germination of the smut spores, tq 

 (.'xi)lain the phenomena in maize smut and to understand them correctly, if the portion of the 

 development of smut fungi enacted saprophytically did not furnish the natural explanation for 

 all details ? It is .scarcely ])ossil)le to find anywhere in the whole domain of infectious diseases 

 a more complete or finer picture of this most striking phenomenon as it exists most clearly here 

 in the etiology of the maize smut. And not less clear has become the understanding of the, 

 smut forms living in our grains which propagate their germs of infection in the soil by sapro-, 

 phytic nutrition and especially in manured soil, in such a way that infectiort of the germinating 

 seedling may therclw be understood and the significance of manure for the occurrence of smut 

 diseases in grain as agriculturists have always emphasized is shown in the proper light. 



Certainly, however, the phenomena of blossom infection are not less convincing and clear. 

 In them the smut germs find their nutrient su.bstrata in the secretion of the stigma and the 

 exudation of honey, which are as favorable as possible for germination, development and propa- 

 gation of the germs of infection. 



It took a long time, more than the lapse of twenty years, to make possible the obtaining 

 of the explanations here given concerning the biology of the smut fungi, their infection, th^ 

 phenomena of the disease and the natural distribution of smut fungi on saprophytic substrata. 

 It was not easv to find in the separate cases the right road which would lead to this goal. 



It should be noticed here, however, that .the universal end of the new investigations, how- 

 ever successful they have proved to be in the cases already carried on, has not in any way been 

 reached and that still many separate experiments must be carried out in order to obtain the 



