ing to which the fungi living parasitically were dependent alone upon the proper host plants for 

 their development, has now been completely upset. Even smut fungi, the most specific of all 

 parasites, have been shown to be only facultatively parasitic. Therefore all doubt is cleared away 

 and parasitism itself can not be considered to be anything else than a phenomenon which, simply 

 accommodated to circumstances and more or less matured, appears in the different forms of 

 parasites. 



The new forms, occurring in saprophytic nutrition, supplement the picture of morphologic 

 forms of these parasitic fungi and make of it an homogeneous whole. Aside from the mor- 

 phologically biological side first emphasized, the pathological especially receives now its true valu- 

 ation. Only in the new forms, shown in the saprophytic life of our fungi, is it first possible to 

 form a natural idea of how these fungi become effective as parasites. Instead of the few, weak 

 sprouting spores in water, new spore forms appear which mature saprophytically in unceasing 

 abundance and which, because of unweakened energy for development, are able to seize upon 

 nutritive plants and to attack them successfully. 



Infection experiments with this newly acquired material of infection germs were planned 

 soon after its discovery. First of all three forms of host plants were chosen for the experiments, 

 — first, Indian millet ; second, oats ; and third, maize, together with the forms of smut belonging 

 to them^ 



For these infection experiments with the host plants named, at first only budding conidia 

 were used which had Ijeen developed in nutrient solutions and kept there more than a month, con- 

 stantly developing and sprouting. The virulence of this material was tested and, in each case, 

 after budding had ceased, germination of the bud conidia which were to be used produced 

 strong germinating tubes. The bud conidia of Indian millet were sprayed on the sprouting 

 seed in dilute nutrient solution by means of an atomizer, in the smallest drops possible. This infec- 

 tion of the young germinating seedlings resulted in the autumn in as much as 70% of smutted 

 plants. For this kind of infection Indian millet is better suited than other experimental plants 

 because of the slow growth of its germinating seedlings and further it was here easily possible 

 to determine the limits within which infection is efifective in the growing germinating seedlings. 

 Seedlings when just sprouting were proved to be the most susceptible. Susceptibility decreased 

 with the further lengthening of the germinating seedlings and was ended when they had grown 

 some cm out of the sheath. Penetration of conidia into the germinating seedling, sprayed on as 

 descrijjed above, was easily determined by observation, since the penetrating germinating tubes 

 leave a noticeably large hole at the juncture of the two epidermal cells'^ The further penetra- 

 tion of the germinating tubes through the epidermis into the interior of the tissue may be fol- 

 lowed without difficulty. 



With the results obtained with this corn and, in the same way with the succeeding experi- 

 mental plants, it was proved incontestibly that infection germs produced in artificial substrata 

 are most highly capable of infecting the host plants. 



(1) Compare the discussions in Part XI of this work. 



(2) See the drawings on the plates in Part XI. 



