CORN SMUTS AND THEIR PROPAGATION 147 



mode of conveyance of pollen from flower to flower is known — 

 by water. Is it possible that smut spores can be similarly 

 carried from diseased to healthy plants ? Brefeld has satisfied 

 himself that in the case of Doassanira and other smut genera 

 found infecting water-plants like Alisma and Sagittaria, the 

 conidia reach the submerged young leaves of the host plant 

 by means of water. Imitating the terms used in pollination, 

 one might say that the host plants are anemosporous, ento- 

 mosporous, and hydrosporous according as the smut spores 

 reach the host by wind, insect, or water respectively. 



The relationship of the millet to its smut fungus (Ustilago 

 Sorghi) is interesting. Evidence is not yet sufficient to decide 

 whether the millet flowers, like those of barley and wheat, 

 can be infected. The evidence goes to show that in millet 

 (Sorghum), Panicum, and Setaria, infection through the flower 

 is rare or absent. The seedlings, however, like those, of oats, 

 are infectible, and the result is not evident until the millet 

 comes into flower. If the millet seedling grows very quickly 

 the smut mycelium which has already " taken " cannot grow 

 fast enough to reach the growing point, and though the fungus 

 is in the joints of the millet stem, the inflorescence itself appears 

 healthy. If, however, as soon as the healthy flowers appear, 

 the plant is cut across at about two-thirds its height, side 

 shoots arise, and these, becoming occupied by the smut 

 mycelium from the nodes, give rise in their flowers to smut. 

 Further, if old seed of millet be sown and, when sprouting, 

 be infected artificially, the slower rate of growth of this old 

 seed allows the smut mycelium to reach the growing point. 

 In such cases the millet flowers on appearing are smutted 

 to such an extent that no single flower escapes. Old seed of 

 barley and wheat, similarly treated, gave no trace of successful 

 infection, i.e. retardation of rate of growth of barley and wheat 

 by the use of old seed does not help the smut mycelium to 

 intrude itself into their growing points, because, as we know, 

 the grains when sprouting are not infectible, and there is 

 thus no mycelium in the host to be favoured by its slower 

 rate of growth. 



The now well-known discovery of Hellriegel that beans, 

 clover, lupine, and other Leguminosce possess the power, 

 through the presence of microbes, known as Rhizobice, living 

 parasitically in their roots and forming root nodules, of fixing 



