368 
Journal of Agricultural Research 
Vol. II, No. s 
SUMMARY 
(1) The head smut of sorghum, Sorosporium reilianum (Kuhn) McAl- 
pine, was first reported from Egypt in 1868. It has been found to be a 
destructive parasite, though not yet of widespread occurrence in this 
country. It occurs also on maize, or Indian corn. 
(2) The organism has been grown in artificial culture. Its growth is 
almost exclusively conidial under favorable conditions, the optimum tem¬ 
perature being 28° to 30° C. As with several others of the Ustilagineae, 
spore-like bodies are occasionally found in older cultures. 
(3) Although perfect sori of the parasite are not usually produced in 
every head of a plant, most of the stools and branches are so affected, 
even when producing no spore-bearing tissue, that the inflorescence is 
sterile and often peculiarly proliferated. This vegetative stimulus results 
also in the development of the lateral buds into branches. 
(4) Histological studies indicate an early period of infection and the 
systemic nature of the disease. The lateral buds carry the infection in 
their meristematic tissue apparently from the time of their formation 
when the culm is starting to differentiate the nodes. 
(5) The work of other investigators, though not conclusive, pointed 
to infection from seed-borne spores and the possibility of applying the 
usual seed-treatment methods for preventing the disease. Both of these 
contentions have been shown to be untenable by an extensive series of 
ecological experiments and exhaustive tests of various sterilizing agents, 
including the use of thermal methods, on the seed. 
(6) Numerous floral inoculations failed to show that the infection was 
produced intraseminally and carried over in the seed to the next crop. 
On the other hand large percentages of infection were repeatedly pro¬ 
duced by inoculation of the seedlings with dry spore material, some 
becoming infected in the greenhouse even after the first leaf had emerged 
from the sheath and begun to turn green. While the process of infection 
has not yet been observed histologically, it is clearly proved that the 
parasite is not carried with the seed, but is wind-distributed in the locality 
in which it occurs, doubtless infecting the seedling from the soil. 
(7) Though widely distributed in the tropical and semitropical coun¬ 
tries of the world, the head smut has been known in this country for only 
about 35 years. Methods of combating it are especially needed in order 
to prevent its spread. Fortunately the widely grown variety, milo, has 
proved immune from all the smuts of sorghum. 
