INTRODUCTION 13 
in all its numberless ramifications. Such a complete 
classification can never be hoped for, inasmuch as the 
plants which now exist are in many cases but scattered 
remnants of groups once much more numerous than 
at present, which have left no recognizable fossil traces. 
Some forms are so much isolated, and have so little in 
common with other groups, that at present any attempt 
to give them their proper place in the system is little 
better than pure guesswork. 
It is thus clear that at present the question is very 
far from settled ; indeed, hardly more than a beginning 
has been made in the establishment of a system which 
can be said to represent real genetic relationships. Our 
present knowledge of the vast majority, even of many 
of the commoner plants, is extremely imperfect, being 
confined often to purely superficial characters. It is 
necessary to investigate thoroughly the structure and 
development of a great many forms before the data 
can be had for constructing a classification which we 
can hope will be permanent, and a beginning only of 
this vast work has yet been made. In addition to the 
careful structural study of the existing plants, a thor- 
ough examination of the fossil species is necessary, 
involving even more arduous labor than does the in- 
vestigation of living forms. Palzo-botany has already 
yielded results of the greatest importance, and it is but 
reasonable to hope that further investigations will add 
much to the materials already accumulated. These 
researches must, however, consist of something more 
than mere collecting and naming of dubious fragments. 
What is imperative is a more complete knowledge 
of the remains already discovered, rather than the 
