-o BIOCHEMICAL SYSTEMATICS 



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recorded history into large or small time periods according to the 

 importance or significance of the events surveyed. 



Botanical historians have also recognized the special signifi- 

 cance of certain contributions in making possible the development of 

 new vistas in botany. Greene (1909) in his Landmarks of Botanical 

 History emphasized the major early descriptive developments in 

 taxonomic botany, particularly as related to specific individuals and 

 their contributions to systematics. Beginning with prehistoric time, he 

 recognized as foremost (1) the descriptive contributions of Aristotle 

 and Theophrastus (followed by a long quiescence up to the fifteenth 

 century), (2) the significance of the observations of the herbalists 

 Tragus, Brunfels, Bauhin, et al of the sixteenth century, (3) the first 

 distinction of the monocots and dicots by John Ray in 1703, (4) 

 recognition of sexual characters and their significance by Linnaeus and 

 others in the mid-eighteenth century, and so on. Greene purposely 

 selected the word "Landmarks" in his published title since he recog- 

 nized "the impossibility of any such thing as a complete and faithful 

 history of any period when once that period is past." 



While such a treatment of botanical history might be sufficient 

 to show the major descriptive phases, it seems that from a dynamic- 

 developmental point of view (in the historical sense) taxonomic history, 

 beginning with Aristotle, can be logically divided into four or five 

 major periods, each of which is terminated (or initiated as the case may 

 be) by some major "breakthrough" in scientific thought or through the 

 development of techniques which have permitted the acquisition 

 of new data (Table 3.1). 



Different writers might recognize yet other "breakthroughs 

 than those hsted below, but we beheve that few readers will argue 

 about the impact of each on taxonomic practice and thought. 



It should be obvious that the present treatment of taxonomic 

 history in no way supposes that the vahd techniques or methods 

 of any prior period give way to those of another. Rather the methods 

 and ideas of succeeding periods are usually superimposed on the 

 pre-existing framework; and all are necessary (or at least have so far 

 been found necessary) in our efforts to obtain an "ultimate" phyloge- 

 netic system of classification. 



These periods of botanical history have been treated exten- 

 sively by a number of writers. Greene (1909) treated essentially the 

 Megamorphic Period; Sachs (1890) treated, among others, the Micro- 

 morphic Period; a number of workers have recently reviewed the 

 Evolutionary Period (Constance, 1955; Tax, et al, 1960; among 

 others); certain aspects of the Cytogenetical Period have been 

 adequately reviewed by several workers (Stebbins, 1950; Clausen, 

 1951; Heslop-Harrison, 1953; Constance, 1955; Darlington, 1956; 



