Effects of supernumerary chromosomes on production of pigment in Haplopappus gracilis.

One of the two types of supernumerary chromosomes found in Haplopappus gracilis effects pigment production in the achene walls. When one, two, and four supernumerary chromosomes were added to the basic complement, a corresponding increase in the amount of one type of pigment was found to occur. No overlapping of the effects on pigment production was observed among different numbers of supernumeraries or between the supernumeraries and normal chromosome complement.