._ BIOCHEMICAL SYSTEMATICS 



48 



analysis in a new way-the genetic basis of the expression of chemical 

 characters. It is not expected that knowledge derived from such tech- 

 niques in higher plants will equal that gained from studies of certam 

 microorganisms (in which the focus has been upon biochemical path- 

 ways rather than phylogeny), but important advances will undoubtedly 



be forthcoming. . . 



Among some groups of organisms, whose simple organization 

 limits a morphological basis of systematics, chemical criteria have long 

 been utihzed. Unfortunately for the present argument it seems that 

 bacterial systematics is about as far away from "naturalness" as that 

 of any group of organisms, and chemical criteria have failed to produce 

 a natural system. According to Van Niel (1946): 



Now the fact that the bacteria also have gradually been assigned to 

 famiUes, orders, and classes does not imply that our understanding of 

 their phylogeny is on approximately the same level as our understand- 

 ing of the plants and animals, in spite of the close resemblance of the 

 structure of the systems of classification. Bacterial taxonomy is far 

 more similar to Linnaeus' original system of the plants, 



However there are special reasons why this situation is to be expected 



in bacterial taxonomy. , , i , u- 



Among certain groups of lower plants, notably the algae, bio- 

 chemical criteria, especially the pigment complement and the principal 

 photosynthetic products, have been given a considerable amount ot 

 weight, and it is probably correct to say that such criteria were im- 

 portant factors in the recent revision of algal taxonomy at the highest 

 level Even in this situation the biochemical information was usually 

 applied negatively, that is, not to show relationship but to support 

 non-relationship. It exposed problems too, for example, m the case ot 

 the siphonaceous alga, Vaucheria, now placed, somewhat conspicu- 

 ously, in the Chrysophyta (Smith, 1950). 



Some preliminary considerations of the 



APPLICATIONS OF BIOCHEMISTRY TO SYSTEMATICS 



Moritz (1958) in a review of plant serology called attention to 

 the fact that serology may make contributions to both major and 

 minor systematic categories; that is, at the family, order, or higher 

 taxon level (major); or to the systematics of genera, species, and 

 infraspecific categories (minor). What is true of serology, itself essen- 

 tially a biochemical method, is true of biochemical contributions m 



