INTRODUCTION TO BIOCHEMICAL SYSTEMATICS 45 



ships are regular. The advantage of the biochemical characters as 

 opposed to morphological characters is presumed to lie in the fact that 

 the biochemical characters are affected in general only in a quantita- 

 tive way by modifiers while many morphological characters (for 

 example, leaf form) may be influenced quaHtatively by numerous 

 modifiers, many of which exert their effect in a cryptic way. Perhaps 

 this generaHzation may prove invahd, but it is offered tentatively on 

 the basis of our personal experience with Baptisia hybrids to date and 

 the much larger background of evidence from biochemical genetics 

 in general. 



Historically, interest in the application of chemistry to sys- 

 tematics goes back almost 150 years. In some of the writings of 

 A. P. de Candolle, as Hegnauer (1958) has noted, considerable atten- 

 tion was given to the chemical properties of plants as correlated with 

 their morphological characters. Examples from de Candolle cited by 

 Hegnauer were the observations that all Cinchona species aided fever, 

 all Pinus species produced terpenes, all Amentifera had astringent 

 bark and all Convolvulaceae were laxative. However, since it was not 

 possible before Darwin's time to accumulate any large amount of 

 chemical data, and since the theoretical implications from the later 

 fields of genetics, evolution, and comparative biochemistry were lack- 

 ing, it is understandable why little interest was displayed. In fact, 

 more often than not, chemical characters seemed to complicate the 

 existing taxonomic systems. An example of what may have been the 

 prevailing pre-Darwinian attitude is the statement by John Lindley 

 in his preface to Vegetable Kingdom, quoted by Gibbs (1958): 



In the first place such matters belong to Chemistry, and not to Botany; 

 secondly, it does not appear possible to connect them with any known 

 principle of botanical classification; and, moreover, the extremely un- 

 steady conditions of the opinions of chemists themselves upon the re- 

 sults of their own researches, would render the introduction of the 

 supposed results of chemists embarrassing rather than advantageous. 



Yet, in 1886, twenty-eight years after the appearance of the 

 Darwin- Wallace papers, Helen C. De S. Abbotfi published a paper 

 entitled. Certain Chemical Constituents of Plants Considered in Re- 

 lation to Their Morphology and Evolution. After noting that Haeckel 

 had divided the flowering plants into three groups: those with sim- 

 plicity of floral elements, those with multiplicity of floral elements, 

 and those with condensation of floral elements; she stated that 



1 Helen Abbott Michael's scientific and philosophical writings, including the 

 reference cited, may be found in Studies on Plant Chemistry and Literary Papers by 

 Helen Abbott Michael. The Riverside Press, Cambridge, 1907. 



