392 
H. F. Wernham. 
tendency to the herbaceous habit which we have observed among 
the higher members of many series. 
Many of the less advanced types may be as vitally efficient in 
their equipment as their descendants. In some cases, indeed, the 
ancestry may be more “ successful ” than the progeny; and the latter 
may be, if not on the way to extinction, at any rate considerably 
restricted in numbers and distribution. This is the case with those 
examples of special complexity which, like Asclepiads, Candolleaceie, 
etc., represent what we may term “ experiments ” of evolution, 
efforts attended by only partial or strictly limited success. Their 
very complexity militates against the wide-spread success of such 
forms. Such mechanisms, on the other hand, as occur in the floral 
parts of Compositae, for example, entail a minimum of “ effort” for 
their production. They are the direct result, in fact, of the mere 
growth and development of the floral parts; yet they are at the 
same time eminently efficient for the performance of the vital 
functions of the production, protection and dispersal of the seed. 
The simpler the structure, the more likely it will be to persist 
in the course of descent, so long as it is associated with a maximum 
of efficiency ; whence has resulted the pre-eminent success of the 
Campanulatae-Compositae branch of the evolutionary tree. 
It is the evolution of this nice balance between simplicity of 
structure—economy in its widest sense—and efficiency of per¬ 
formance which constitutes “ general progress”; and the principle 
of progress underlies all the general tendencies and determines all 
the main evolutionary lines. 
“ Biological” and “ Fortuitous ” Characters. Each line repre¬ 
sents the progressive acquisition of some character or set of 
characters advantageous biologically. Progressive advance being the 
determining influence of the evolutionary story with which we are 
dealing, biological characters —i.e., such as are in direct relation to 
some vital function or advantage—cannot be neglected in any natural 
system of classification, however dangerous they may be in this 
connection. 
For extreme caution must be employed in the use of biological 
characters in the determination of affinities. Plant-forms of widely- 
differing ancestry have undoubtedly tended to the acquisition of the 
same character of obvious advantage. To take an example from 
the many we have encountered in the course of our investigations, 
the aggregation of flowers into capitulate inflorescences is a 
character directly advantageous from the aspect of the biological 
