BIOCHEMICAL STUDIES OF HYBRIDS 325 



occur. However, since the peak flowering times of these two species 

 are several weeks apart in areas where the species occur together, this 

 time factor may account for their reproductive isolation. 



Hybrids involving Baptisia nuttalliana and all three other 

 species have now been discovered. B. nuttalliana hybridizes exten- 

 sively with B. leucophaea in the area around Huntsville, Texas, and 

 at other sites in Texas and Louisiana. These hybrid swarms are 

 readily recognized, and in this case it is the biochemical corroboration 

 which is more difficult to obtain. Of those substances available at this 

 time B. nuttalliana contains a number of compounds in common with 

 B. leucophaea and/or B. sphaerocarpa. In both types of hybrids, 

 therefore, while B. nuttalliana chemical components can be docu- 

 mented readily, fewer species-specific contributions from the other 

 partner are available. 



Large populations of B. sphaerocarpa and B. nuttalliana have 

 not been found together thus far, although they probably occur. Con- 

 sequently, hybrids involving these two species are found in situations 

 wherein one species (often B. sphaerocarpa) seems to be introduced, 

 as along a roadside in the range of the other. Several such populations 

 have been located, always represented by a very few plants of, usually, 

 B. sphaerocarpa, some obvious hybrids, and more numerous, usually, 

 B. nuttalliana. On this basis, it appears that these two species 

 hybridize freely when they occur together. It is interesting and sugges- 

 tive that the seed pods of B. sphaerocarpa are hard, spherical, and 

 just about the size suited to becoming wedged into the tire grooves of 

 vehicles. 



A few definite hybrids between B. nuttalliana and B. leucantha 

 are known; the hybrid was suspected on morphological grounds and 

 definitely established by chromatography (Fig. 15-2d). 



In the southeastern United States other complex situations 

 involving hybridization of several species of Baptisia occur. In some 

 instances chromatographic evidence is essential to establish the hy- 

 brid nature of a particular specimen. For example, two definite hy- 

 brids have been found in a population of Baptisia lanceolata, B. alba 

 and B. pendula. The last two species are white flowered and some- 

 what similar morphologically, but they are chromatographically 

 distinct. The hybrids, which involve B. lanceolata plus one or the 

 other of the white flowered species, are morphologically similar. 

 Chromatograms establish certainly the fact that one hybrid is B. 

 lanceolata x B. alba; the other is B. lanceolata X B. pendula. (Alston 

 et al, 1962). 



Baptisia alba also hybridizes with B. perfoliata, B. tinctoria 

 (Duncan, 1962) and probably certain white flowered species. Despite 

 the striking differences between B. alba (Fig. 15-2h) and B. lanceolata 



