GRAMINEOUS CROPS. 101 



gemmation, which may go on indefinitely — so long as the 

 medium in which the spores live is suitable for this 

 method of reproduction. In this respect (i.e., reproduction 

 by gemmation) Ustilago carbo resembles the cells of 

 Torula cerevisice (the yeast organism), and better still those 

 of Torula apiculatus. The secondary spores continue pro- 

 ducing the same spores, or give rise to germ-tubes (hyphse, 

 Fig. 39 D) which germinate on, and produce a mycelium 

 within, the tissues of the host-plant. It is possible that 

 conjugation i takes place between the spores of the smut 

 fungus, for this method of reproduction is not uncommon 

 in the genus Ustilago. The spores of the smut fungus are 

 to be found in the soil, air, and on the seeds of oats, barley, 

 and wheat before sowing. 



Prevention. — (1) Destroy all affected ears at the earliest 

 stage when the disease is visible, and before the spores 

 have ripened. (2) " Burn all smutted grasses." 



Cure. — (1) The author has shown that steeping the 

 grain before sowing in a 2 per cent, solution of iron 

 sulphate for three or four hours entirely destroys any 

 fungal spores which may be upon the seeds ; and this 

 method does not injure the germinating power of the 

 grain. (2) A solution of copper sulphate ^ has often been 

 recommended for the same purpose, but there is little 

 doubt that this reagent frequently destroys the germinat- 

 ing power of seeds (Biedermann's Centralblatt fiir Agri- 

 cultur-Chemie, 1886, p. 766). Mr. J. L. Jensen (Journ. 

 Roy. Agric. Society, 1888, p. 397) says that "dressing 

 cereals with copper sulphate in the usual manner against 

 smut and bunt causes, as a rule, a waste of the seed-corn. 



1 The production of a spore by the union of two " like " cells. 



2 1 lb. dissolved in 5 quarts of water for 4 bushels of grain. 



