OATS, AND BARLEY. 



95 



We will now take a dwarfed and diseased cluster of grains and 

 chaffy scales from a wheat-spike and magnify with a lens five 

 diameters. We now see it as at D. The chafty scales are rent 

 and torn, and from every fissure the fine sooty powder is seen 

 bursting out. If the cluster or spikelet is cut across as at E^ it 

 will be noticed that the whole farinaceous material of the interior 

 has been replaced by one compact mass of fine black dust. The 

 upper part of the stem of the corn^ and the scales and grains 



Spikelet of Wheat (D) atid transz'efse section {E) ijivaded by the 



Smut fungus^ enlarged 5 diameters. Disease pustules of 



ditto, enlarged 25 diameters. 



alike, are infested and choked by the sooty powder. If we take a 

 fragment of one of the chaff" scales, and magnify it with a micro- 

 scope 25 diameters, we shall see numerous cracks, some large, 

 others small, as at F, and from every crack the fine jet black 

 powder will be seen bursting out from the inside. 



Every grain of this black powder is an inconceivably minute 

 spore or seed of the Smut fungus. In an early stage of the 

 disease, in a state seldom noticed by farmers, the fungus is colour- 

 less ; it grows within the stems of corn as fine transparent threads, 

 immeasurably finer than any spider's thread. These threads at 

 length reach the ears, the scales, and the infant grains. Here they 

 form within the substance of the plant a whitish viscous mass of 



