SORGHUM SMUTS AND VARIETAL RESISTANCE 19 
suited in a speedy multiplication of so-called varieties. Fully 200 
names have been recorded for various saccharine sorghums, although 
it is doubtful whether the number of actual varieties was ever more 
than 20. 
Most of the common varieties of sorgo fall into one of the four 
following groups: Black Amber, Red Amber, Orange, and Sumac. 
Data on the infection obtained on the various strains and varieties 
are presented in Table 2, in which the varieties are separated into 
these groups. 
Early Amber, the original Black Amber strain, was supposedly de- 
veloped in Indiana from the first Chinese importation (1). More 
recently other varieties or strains have been developed, such as 
Minnesota Amber, Dakota Amber, Improved Amber, and Earliest 
Black. Folger, or Folger Early, is also a strain of the Early Amber, 
especially improved as a sirup variety. Collier and McLean are 
closely related varieties. These are, for the most part, strains or 
varieties selected from the original Early Amber, differing perhaps 
in earliness and other characteristics. 
Altogether, 21 different strains of the Black Amber group of sorgos 
were inoculated with the spores of Sphacelotheca sorghi. These 
strains included the more or less distinct varieties of Amber sorgo, 
such as Dakota Amber, Minnesota Amber, Early Amber, Folger 
Early, Collier, and McLean. With two apparent exceptions all the 
strains proved susceptible, generally showing high percentages of 
infection. 
Some of the highest infections obtained with any sorghums were 
obtained on strains of this group. It was not uncommon to obtain 
infection running above 40 per cent. It is especially interesting to 
note the high percentages of infection obtained at Amarillo and 
Manhattan with Folger Early (F. C. I. No. 1480). At Amarillo 
50.8 per cent out of a total of 256 heads were infected, and at Man- 
hattan 61.6 per cent of infection was obtained out of a total of 73 
heads. These percentages of infection equal or suroass those ob- 
tained with the same or other strains at the other stations. 
The varieties of the Red Amber group are very similar in growth 
to Black Amber but have red instead of black glumes. Five strains 
of the Red Amber group were grown, two under the name of Early 
Rose and three as Red Amber. In general, Early Rose showed a 
high percentage of infection, running up to 60.4 per cent in one case. 
Red Amber generally showed less infection than Black Amber, and 
157 plants of one strain at Columbia, Mo., in 1918 showed no in- 
fection whatever. The strains at Manhattan and Amarillo showed 
comparatively low percentages of infection. , 
The Orange sorgos constitute a distinct group. They are of South 
African origin and can be traced to one of the Wray introductions. 
They differ from the Amber group in having larger and heavier 
stems and more abundant leaves. The panicles also are much more 
compact than those of Amber. Several strains have been developed, 
such as Kansas Orange, Late Orange, Improved Orange, and Peren- 
nial Orange. Colman is a variety which is said to have originated 
as a hybrid between Early Amber and Orange sorgo, but is more 
closely related to Orange than to Early Amber. Planter and Silver- 
top are closely related varieties. 
