BIOCHEMICAL STUDIES OF HYBRIDS 



319 



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Fig. 15-2 (cont.) Most spots are species-specific; (e) B. pendula (practically indistinguish- 

 able from B. leucantha); (f) B. lanceolata; (g) B. perfoliata; (h) B. alba. 



(In text, p. 317, references to the types of interspecific hybrids involving B. 

 leucantha are symbolized as "eL"). 



(these are often in low concentrations and may be below 

 the threshold of detection in some instances) 

 (4) hybrid-specific substances 



A few substances of type 4 were regularly present in hybrid types but 

 not in the parental types. It was not possible in the original work to 

 determine whether the "hybrid substances" were de novo products 

 of the hybrid's gene combinations or accumulations of substances 

 normally produced in small amounts in one or both parents (compare 

 Schwarze, p. 315). Subsequently, it has been found that all four of 

 the so-called "hybrid substances" are actually typically produced by 



