THE COMPOSITION OF A HYBRIDIZING POPULATION OF BAPTISIA SPHAEROCARPA AND BAPTISIA LEUCOPHAEA.

Abstract

This study of interspecific hybridization in a single large population of Baptisia leucophaea and B. sphaerocarpa represents the first time such an extensive comparison of morphological and chemical criteria has been reported. In this investigation each mature plant in a plot 300 ft X 240 ft, a total of 1170 plants, was located precisely in the population, collected, and analyzed by use of a morphological hybrid index and a second hybrid index based primarily on flavonoid chemistry. This same hybrid combination was the first of many types of Baptisia hybrids to be examined by combined morphological and chemical methods (Turner and Alston, 1959), but only 20 plants were examined in that original work. Subsequently, two different types of population studies have been reported, but one of these was a limited study of a trihybrid population (Alston and Turner, 1962) and the other involved several different small populations because no single large hybridizing population was available (McHale and Alston, 1964). This present study of Baptisia hybridization is the first in which the chemical identities of most of the compounds utilized have been known. In their study of natural hybridization among three species of Baptisia, Alston and Turner (1962) reported striking disagreement between the morphological and chemical analyses. The chief difficulty was considered to stem from the unsuccessful attempt to construct a trihybrid morphological index which did not distort the data and lead to an inference of much more com-