314 



BIOCHEMICAL SYSTEMATICS 



Finally, in another cross involving the species E. maidenii and 

 E. rubida there is an example of dominance for the absence of a com- 

 ponent. E. rubida contains a fluorescent substance which is absent 

 from E. maidenii and from all the Fi hybrids (five in number). 



Bannister et al. (1959) also reported a study of hybrids which 

 included both morphological and chemical characters. These investi- 

 gators concentrated on certain of the essential oils, such as a-pinene 

 and /8-pinene. The species involved were Pinus attenuata, P. radiata, 

 and some verified and putative hybrids thereof. The method of assay- 

 ing the relative content of a- and /5-pinene of the oleoresin was by use 

 of gas chromatography. This technique ought to become increasingly 



