Studies of chromosome knob numbers of the maize varieties of Latin America have been continued with the following results:
Although the sampling of individual countries is still far from adequate, the data tend to support the previous conclusion, that low-knob varieties are confined in Central America to Western Guatemala and to the immediately adjoining regions in Mexico. In all other parts of Central America and Mexico and in Cuba as well, only high-knob varieties have been encountered. Western Guatemala and the adjoining state of Chiapas in Mexico continues to appear to be the center of maize diversity in Central America.
It appears also that Paraguay must now be added to Peru and Bolivia as a region of low-knob varieties in South America. Although only five varieties from Paraguay have been examined cytologically, the majority of varieties collected are of the same general type as these and will probably prove to have but few knobs.
Dr. Hugh C. Cutler has now spent more than a year in Brazil, Paraguay and Bolivia collecting native corn varieties and searching for wild maize. His first goal is being successfully achieved; the second is still elusive. Several reports of maize growing in the wild have been investigated with wholly negative results. The "wild" maize in each case was either cultivated maize obviously escaped from cultivation or not maize at all. The cultivated corn collected from Paraguay and Southwestern Brazil is of considerable interest. The cobs are quite flexible; the pedicels on both staminate and pistillate spikelets longer than normal.
A variety of maize obtained from Amantina Island in Lake Titicaca in Peru at an altitude of about 12,500 feet, probably the highest altitude at which corn is grown in any part of the world has proved to be early and cold-resistant. These characters my make it valuable for plant breeding in spite of the fact that it is very susceptible to smut.
P. C. Mangelsdorf and James W. Cameron