A single smut ball of average size contains a sufficient number of spores to give one for each grain of wheat in five or six bushels.

It takes eight smut spores to equal the diameter of a human hair.

Normal wheat grains from an infected field may have so many spores lodged on their surface as to give them a dark color, but other grains which show no difference in color to the naked eye may still contain a sufficient number of spores to produce a smutty crop if seed treatment is not practised.
"When living smut spores are introduced into the soil with the seed wheat, or exist in the soil in which smut-free wheat is sown, a certain percentage of the wheat plants are likely to become infected.

The smut spore germinates and produces first a stage of the smut plant in the soil.

This first stage never infects a young seedling direct, but gives rise to secondary spores, or sporida, from which infection threads may arise and penetrate the shoot of a young seedling and reach the growing point.