334 Barber. — Cup res sin oxy Ion vec tense. 
up to that date might, from their diagnoses, very well belong 
to different parts of one and the same tree b 
Many of the characters formerly used in descriptions, such 
as the width of the annual rings, numbers and heights of 
medullary rays, sizes of tracheides, thickness of walls, &c., 
have now been demonstrated to differ as much in the same 
species as in different genera. To illustrate this fact, Kraus 
carefully examined a fossil stem with branch attached. He 
showed that these two parts differed so widely in the 
characters just enumerated that, following the lines of the 
old-time diagnoses, they would have to be put into well- 
separated ‘ species.’ The detailed study which has led to 
these results has indeed characterized the period inaugurated 
by Kraus (1864). Sanio, Schroeter, Schmalhausen, Russow, 
Kny, Schulze, Wille and others, have supplemented their 
general comparative study of many forms by a minute, 
intensive examination of individual species. In the process 
the earlier descriptions have been thrown into confusion, but 
the path has been marked out along which any work of value 
in this field must be followed. 
It is true that these writers have shaken, one by one, the 
pillars upon which the classification of Coniferous woods has 
been erected ; their work has, in this sense, been mainly 
destructive. The characters of absolute importance have, 
however, been rigidly defined, new characters have been 
raised from relative to absolute value ; and, what is perhaps 
of equal importance, the conditions have been determined 
under which the characters of relative value may be used 
in diagnoses. These conditions include a knowledge of the 
age and morphological character of the part as well as the 
mode of petrifaction. It is nevertheless only too apparent 
that the work of reconstruction has only commenced, and any 
description of fossil wood which is to be of use in the future 
must include an exhaustive analysis of all the characters, both 
absolute and relative, which have not been proved to be purely 
fanciful. 
1 Kraus, 1. c. 
