326 BIOCHEMICAL SYSTEMATICS 



(Fig. 15-2f), the hybrids between either of these species and B. 

 perfoliata (Fig. 15-2g) are difficult to distinguish when not in flower. 

 Since these three species may be found together and hybridization 

 between them also occurs, chromatographic evidence is not only 

 useful but in some instances essential to the clarification of a given 

 hybrid type or the structure of a population. 



The number of species-specific compounds which may be 

 utilized both in the study of natural hybridization in Baptisia and in 

 establishing species affinities is increasing. Brehm (1962) has carried 

 out an extensive study of variation in several categories of substances 

 in Baptisia leucophaea, in different organs, at different developmental 

 stages, in individuals of a single population, and in various popula- 

 tions throughout its range. Of the compounds investigated, the 

 miscellaneous substances of leaves and flowers demonstrable in ultra- 

 violet light, ammonia vapor, and by use of general phenol-detecting 

 reagents are by far the most useful. The variation in the lupine-type 

 alkaloids from plant to plant renders these compounds of relatively 

 little use in population analyses. Surprisingly, the free amino acid 

 patterns of seeds, stems, leaves, and flowers are not only markedly 

 similar, but furthermore the patterns of the different species examined 

 so far are notable for their similarities rather than differences. 

 Thus, the free amino acids are of little use in population studies, 

 but for unexpected reasons, since there was occasion to expect the 

 patterns to vary rather greatly within a species (Chapter 6). 



In summary we believe that biochemical comparisons have 

 provided us with new and informative data and offer considerable 

 promise in studies of natural hybridization and problems related 

 thereto including perhaps a new method of documenting introgressive 

 and transgressive hybridization. It is possible that the genus Baptisia 

 is particularly well suited to such an approach and that its repository of 

 species-specific compounds is not representative of hybridizing species 

 in general. Even in Baptisia some hybrids cannot be resolved by 

 chromatography. Although we have not discussed infra-specific 

 chemical variation in Baptisia, preliminary studies indicate that in 

 certain species (for example, B. nuttalUana) information can be ob- 

 tained from intensive populational sampling for the presence of 

 particular compounds found to be non-constant in the species. It is 

 not likely that such methods may be applied as readily to species which 

 have become established and which are suspected to be of hybrid 

 origin. Subsequent selection of new gene combinations plus mutations 

 may have highly modified or even obliterated the hybrid type pattern. 

 However, it is also possible that in certain fortunate circumstances 

 chromatographic analyses may disclose evidence of past hybridization. 



