52 



This very obvious example of infection in the blossoms had been hidden and kept from 

 a full understanding by the fact that the smut in the infected blossoms did not appear in the same 

 year with the ripening of the grain; that rather the germs of infection which hai'c penetrated into 

 the seed lie latent there and develop in the matured and blossoming plants only in the following 

 year, with the germination of the seed. Blossom infection, however, which could be proved 

 with certainty in the pistillate spikes of maize occurred here therefore in a varied form, in that 

 the period of incubation up to the breaking out of the disease, that is, until the spore masses 

 mature, is considerably longer. It is not spanned by three weeks, but is completed only in the 

 second year, following the finished inoculation. In this noteworthy fact lies the peculiarity of the 

 now ascertained blossom infection of our varieties of grain. 



Accordingly, in the occurrence of smut diseases in our grains, we must reckon with two 

 places of infection quite independent of each other; first, the young germinating seedlings, 

 second, the blossoms. We must consider that in separate cases both forms of infection may 

 be effective at the same time, but first one and then the other will be predominantly active. In 

 judging of the natural spread of smut fungi and smut diseases, these recently explained facts are 

 of decided value. 



However, in the details here given only the development of the parasites within their host 

 plants has been considered, the different forms in which infection takes place and also how, 

 from the germs of infection already present, the further development of the smut fungi and 

 of the phenomena of diseases is carried up to the formation of spore masses. 



Now, however, by means of the earlier investigations and cultures reported in Parts V, 

 XI and XII of this work, it has been proved that smut fungi can live not only in the host 

 plants, but that they occur also outside of the host plants on saprophytic substrata and mature 

 there in different and new forms, which have not been observed within the host plants. How- 

 ever well smut fungi, as parasites in the host plants, may show the most complete adjustment 

 to their hosts, which adjustment can be observed only in nature, they are rather not specific 

 parasites, but only facultative ones. They may live and flourish outside the host plants in all 

 substrata to be found in nature. A rapid and active development of the smut fungi takes place 

 in these nutrient substrata and especially an exceedingly abundant increase of the germs. Smut 

 fungi live in nature outside the host plants just exactly as do other saprophytic fungi and their 

 propagation takes place especially where nutrient substrata are present in humus and well 

 manured soils. A saprophytic development results here and also a propagation of the germs. 

 From these places, as in maize smut where air conidia are formed, the germs of infection can 

 be distributed on to the susceptible parts of neighboring host plants. In other cases where air 

 conidia are absent, the germs of the smut fungi, developed and increased in the soil, will attack 

 the young germinating seedlings and produce the phenomena of smut. 



Further, nutrient substrata, independent of soil, for the development of smut fungi, may 

 be found in the secretion of the stigmae and in the honey of plants fertilized by insects. In all 

 such cases saprophytic nutrition of the smut germs introduced in these places may be proved 

 with certainty. 



