THE BASIS OF THE STEM STRUCTURE. 177 



The first serious attempt to construct a system of classifica- 

 tion based upon the anatomical characters of the wood of which 

 I have been able to gain information appears to be that of 

 N. J. C. M tiller, published in I888. 1 In this work sixty-five 

 species are illustrated by means of photomicrographs, and the 

 text details the characters of the wood structure as displayed 

 in the three planes of section commonly employed. The figures 

 accompanying the text are very poor and often misleading, 

 while the efficiency of the work is greatly impaired by the fact 

 that attention is not concentrated upon any one group a few 

 representatives from a rather large number of families being 

 chosen as subjects of investigation. 



From the history of the subject as thus briefly outlined it is 

 clear that for some time past botanists have been aware that 

 sooner or later the anatomical characters of the stem must 

 claim recognition as important factors in taxonomy. The need 

 of such a system of classification as now proposed has been 

 apparent not only in the demands arising from an extensive and 

 varied economic application of numerous kinds of woods, but in 

 the requirements of the palaeobotanist who seeks for some 

 more exact means of defining species and of establishing the 

 relations of fossil woods to those now living, than is to be found 

 in a merely general knowledge of structure. When it is recalled 

 that fossil woods are commonly represented by the more durable 

 parts only a structure from which many of the anatomical 

 details may have been eliminated by the operation of decay or 

 the subsequent alterations attendant upon petrifaction in 

 consequence of which it becomes of the highest importance 

 that the taxonomic value of such characters as are yet recog- 

 nizable should be capable of exact estimation, and that wood 

 applied to economic purposes often requires to be recognized 

 under conditions which render the ordinary means of distinc- 

 tion worthless, it is clear that any system of classification which 

 will admit of a precise limitation of genera and species under 

 all conditions, must possess a high degree of value. 



With respect to the application of such a classification to 

 living species, the view has been entertained that if species 



1 Atlas der Holzstructur und erlauternder Text. 



