190 



BIOCHEMICAL SYSTEMATICS 



However, the relationship of Cephalotaxus to Taxus on mor- 

 phological grounds is not considered to be close. Although formerly 

 included in the Taxaceae, Cephalotaxus is now considered a separate 

 family, Cephalotaxaceae (Buchholz, 1951). In view of this pre- 

 sumed lack of close relationship between Taxus and Cephalotaxus the 

 statement by Hegnauer has less significance. Cyanogenesis in Taxus 

 is not to be considered of systematic significance beyond perhaps 

 additional support for the recognition of varieties. Hegnauer says that 

 since separation of some of the cultivated forms of Taxus may be 

 difficult, cyanogen content may serve as a useful character. This 

 suggestion may be received with some reservation, since the character, 

 unsupported by correlated morphological differences, is of dubious 

 value in delimitation of anything more than a single or perhaps a few 

 genie differences; for example, in Trifolium repens it has been estab- 

 lished that a single dominant gene governs production of the cyano- 

 genetic compound (Wilhams, 1939) and another gene the enzyme re- 

 quired to hydrolyse the cyanogen (Atwood and Sullivan, 1943). If we 

 knew sufficiently well, the biochemistry of the species and its individ- 

 uals we might regard plants as biochemical individuals just as 

 R. J. Wilhams and Reichert before him regard individuals as bio- 

 chemically unique. 1 



1 Reichert, 1919. "Recently data have been rapidly accumulating along many and 

 diverse lines of investigation which collectively indicate that every individual is a chemical 

 entity that differs in characteristic particulars from each other." 



