vi PREFACE 



which the field is founded and with Hmited knowledge of modem 

 work in systematics. Chapters II through IV are written primarily 

 for the nonsystematist. We ask the indulgence of the well-informed 

 if this introductory matter reiterates much that has already been 

 written on the subject. 



At the present stage of development, plant biochemical sys- 

 tematics is a difficult field to survey. It will be noted that nowhere in 

 the book is there a phylogenetic tree constructed out of chemical 

 correlations. Perhaps contrary to the expectation of some readers, we 

 do not see that even the beginnings of such a system are justified. Thus 

 the decision to organize the chapters about major groups of chemical 

 constituents rather than to focus upon taxonomic systems of catego- 

 ries is based upon our firm belief that it is more useful to consider 

 various "natural" chemical groups somewhat critically relevant to 

 their present and potential systematic value than to draw a series of 

 taxonomic judgments out of the usually fragmentary biochemical 

 data at hand. The latter approach has been used, at least eclectically, 

 by others, to no great advantage. 



The writers cannot regard present limited biochemical data 

 as favoring one or another of the systems such as those of Engler and 

 Prantl, Bessey, Hutchinson, etc. Much of the literature in biochemi- 

 cal systematics includes references by the authors to competing sys- 

 tems when the data bear upon the systematic relationships of higher 

 categories, but in general the individual issue concerns only a small 

 part of the taxonomic whole, and the chemical data now available are 

 often quite limited. 



Some readers may be puzzled by the fact that we speak else- 

 where of taxonomists who have no interest in phylogeny. The non- 

 taxonomist may be least capable of understanding this situation. 

 Nevertheless, professional taxonomists exist who favor the exclusion 

 of phylogeny from taxonomy. Similarly, although authoritative docu- 

 mentation from the literature is not available we have heard promi- 

 nent biologists express the belief that biochemistry could never make 

 a contribution to systematics since, e.g., nicotine and certain other 

 substances occur in obviously unrelated plant groups. Such argu- 

 ments as the latter may be transparent, but they are not fictitious, 

 and therefore some attention is given to answering them in the text. 



We believe that the intellectual, technical and perhaps even 

 psychological gap (not intended to be construed as hierarchical in 

 nature) between systematics and chemistry has been the main factor 

 in delaying the maturity of biochemical systematics as a natural 

 discipline. Biochemical systematic studies of the present are often not 

 markedly different from those of 30 years ago. Modern statements 



