PLANT TAXONOMY 



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Table 3-1. The major historical or developmental periods of systematic biology. 



Period 



Time 



1. Megamorphic 



2. Micromorphic 



3. Evolutionary 



ca. 400 B.C. to ca. 1700 a.d. 

 (Beginning with Aristotle's time 

 and continuing to Leeuwen- 

 hoek's invention of the micro- 

 scope.) 



ca. 1700 to ca. 1860. 

 (Beginning with Leeuwenhoek 

 and continuing to Darwin's pub- 

 lished views on evolution.) 



Characterization 

 of the period 



A terminological-descriptive 

 period characterized by the 

 development of formal group 

 concepts (e.g., families, genera, 

 species, etc.) and the establish- 

 ment of a descriptive language 

 to define these groups better. 



4. Cytogenetical 



5. Biochemical 



ca. 1860 to ca. 1900. 

 (Beginning with Darwin's evo- 

 lutionary theory and extending 

 to the rediscovery of Mendel's 

 laws of inheritance. ) 



ca. 1900 to ca. 1960(7). 

 (Beginning with the rediscovery 

 of Mendel's laws and extending 

 to the present time.) 



Leeuwenhoek's microscope and 

 lens systems made possible the 

 recognition of hitherto unknown 

 microorganisms, the recognition 

 of sexual features, and their sig- 

 nificance and made possible the 

 acquisition of new morphologi- 

 cal data (viz., anatomical em- 

 bryological, palynological, etc.). 



Darwin's theory profoundly 

 affected systematic thinking. 

 Hereafter most classification 

 systems were constructed on a 

 phylogenetic basis. 



ca. 1950(?) to 



-(?). 



(Beginning with the biochemi- 

 cal approach, made possible by 

 the development of rapid and 

 relatively simple techniques 

 such as chromatography, and 

 possibly extending to the deter- 

 mination of the sequences of sub- 

 units of polynucleotides such as 

 DNA and RNA and of proteins. 

 Techniques are already avail- 

 able whereby nucleotide and 

 amino acid sequences can be 

 analyzed.) 



This period is characterized by 

 the detailed application of cyto- 

 genetical data and populational 

 statistics to plant taxa, mostly 

 at the generic, specific, and 

 infraspecific levels. These tech- 

 niques permitted the first truly 

 experimental approach to sys- 

 tematics. 



Characterized in its early stages 

 by the establishment of "bio- 

 chemical profiles" for various 

 plant taxa and their compara- 

 tive use in solving taxonomic 

 problems; in later stages by a 

 comparative biochemical ap- 

 proach that takes into consider- 

 ation metabolic pathways, pro- 

 tein evolution, and comparative 

 enzymology. 



