316 BIOCHEMICAL SYSTEMATICS 



which would not be found in either parent in addition to the products 

 derived from new gene combinations. 



Schwarze says in his discussion (freely translated): 



Outside of economy of metabolites and full regulation of them there 

 are no principles of evolutionary selection. Favorable metabolic 

 mutants thus have positive selective value, but also mutants with 

 metabolic significance which represent neither positive or negative 

 survival value are preserved. Metabolic economy must control their 

 quantities. Possibly, in Phaseolus hybrids, in which P. vulgaris cyto- 

 plasm is under the influence of strange genes, formation of some use- 

 less substances occurs. 



It is interesting that in the Pryor and Bryant study of Euca- 

 lyptus hybrids (discussed earlier), although total oil yield was gen- 

 erally low in the hybrids, the quantities of the minor components was, 

 among the hybrids, very greatly increased in almost every case over 

 that of either parent. 



A biochemical study of natural hybridization in the genus 

 Baptisia (Leguminosae) was initiated recently (Alston and Turner, 

 1959; Turner and Alston, 1959), and rather extensive biochemical 

 documentation of hybridization in this genus has now been acquired 

 (Alston et al, 1962; Alston and Turner, 1962b; Alston and Turner, 

 1963). The first report dealt primarily with Baptisia leucophaea, B. 

 sphaerocarpa and their assumed hybrids. Extensive hybridization be- 

 tween these morphologically quite different species occurs, especially 

 near the Texas Gulf coast. By means of paper chromatography a total 

 of six species-specific chemical components (three for each species) were 

 detected in flower extracts. Then, chromatographic analyses of individ- 

 ual hybrid-type plants disclosed recombination or in some cases simple 

 addition of the species-specific components. The same plants were 

 adjudged hybrids or hybrid derivatives on the basis of morphological 

 characters. The chromatographic evidence of hybridization was con- 

 sidered to be indisputable. Since morphology alone suggested, 

 definitively, hybridization between the two species concerned, the bio- 

 chemical evidence did not provide any further insight into that 

 situation. However, the work firmly established the practicality of a 

 biochemical approach to analyses of more complex hybrid situations. 

 As will be disclosed below, it also paved the way for entirely new 

 methods of analysis of population dynamics and gene flow in naturally 

 hybridizing populations. 



Numerous species of Baptisia are native to eastern North 

 America. Inter-specific hybridization is common in the genus, and the 

 morphological differences between species which hybridize are 



