The determination of chromosome knob numbers in the more important inbred lines of Corn Belt maize was started in the sumer of 1945, of which a preliminary account may be made at this time. To date, approximately thirty inbred lines of dent corn, twelve open pollinated or inbred strains of popcorn, and five North American flints have been examined. Although these numbers are relatively small when compared with the total amount of material available, the results obtained reveal some rather interesting facts. Among the thirty dent corn inbreds studied, knob numbers are found to range from two to nine with a frequency distribution as indicated in figure (1). Knob numbers appear to be correlated with certain morphological characters of the ear. For example, those lines possessing high knob numbers have, in general, a more compressed base, more tapered ears, and higher numbers of rows of kernels than those with low numbers. There is also some evidence indicating that irregular rowing is associated with high knob number. Among the popcorn strains examined, all were found to possess median knob numbers (4-6). The most interesting observation encountered occurred in the 8-10 rowed North American flints which were found to be knobless or nearly so. Of the five lines examined, four were knobless and one contained a single knob. These data, it will be noted, are not entirely in agreement with what one would expect on the basis of the tripsacum hypothesis.
William L. Brown