Multiple Differentiation of Plasmons of Diploid Species of Solanum.

TUDIES of plasmon variations in Epilobium (MICHAELIS 1954; CASPARI 1948), Oenothera ( STINSON 1960; STUBBE 1960), Streptocarpus ( OEHLKERS 1938; OEHLKERS and EBELL 1958), Solanum (KOOPMANS 1951,1952,1954,1955, 1959; BUCK 1960), Clarkia (HIORTH 1948), yeast (EPHRUSSI 1953), and Culex ( LAVEN 1959) have demonstrated that heritable plasmon variations exist and are of evolutionary importance. A further understanding of the role of plasmon variations will require a method for tracing the consecutive steps through which plasmon changes occur. This, in turn, will require that one be able to identify the individual unit characters of which a given plasmon is composed and formulate what might be termed a plasmantype, or description of a plasmon. The analysis presented here is the first step of an attempt to describe such plasmon characters of diploid tuber-bearing species of Solanum. These plants have the advantage that a considerable number of closely related species can be crossed (SWAMINATHAN and HOWARD 1953; HAWKES 1956a; HOWARD 1960; GRUN 1961) to produce fertile hybrids and, therefore, a diversity of genetic and plasmon types can be subject to test.