114 PROF. BOWER : 
structural detail from the Mesozoie Hocks. For it was at the period 
when these were laid down that the immediate ancestors of the Angiosperms 
flourished. 
Methods of enquiry such as these applied to Flowering Plants are equally 
applicable to other divisions of the Vegetable Kingdom. The cogency of 
the results will vary with the variety and consecutiveness of the evidence. 
The criteria of comparison will naturally be different. For instance, in the 
Fungi dependence must be placed on the propagative, rather than the 
vegetative system, while paleontological evidence is virtually absent. In 
the Bryophytes, as also in the Algze, the vegetative system gives greater help 
than in the Fungi: but again paleontological evidence is lacking. Recent 
observations, however, point to the existence of sporogonium-like bodies even 
from the Lower Devonian: thus indicating, on a basis of direct evidence, 
a higher degree of antiquity than had previously been contemplated. 
There remain the Pteridophyta. In them, and particularly in the Filicales, 
evidence from various sources converges, so as to form a wide basis for their 
phyletic arrangement. The results may indeed be held as more effective 
here than in any other large group of Plants. We know from the fossil 
record that organisms rightly ranked as Ferns date back far into the 
Paleozoic Period. Such types, with modifications, may be consecutively 
followed through successive horizons to the Present Day. Comparison shows 
that some, though relatively few of the Ferns now living, correspond to the 
archaic types of the Paleozoic ; while those of successively later horizons are 
represented more and more freely in our present Flora. Finally, the great 
mass of our living Ferns show characters which stamp them as distinctly 
modern. Old though the Filical type undoubtedly is, we conclude from 
inner comparison, as well as from the Fossil Record, that the fullness of its 
development is that which we see in the majority of the living Ferns of the 
Present Day. It is not a type which has stood still, but one which has con- 
sistently advanced: and the advance has been as definite as that of the 
Flowering Plants, but along quite different lines. Thus the Filicales offer 
a singularly instructive field for the application of a phyletic method, so as 
to elicit a really Natural Classification. 
The basis upon which conclusions as to the evolutionary sequence of such 
a group as the Filicales are to be arrived at, is at root that of the Natural 
System of Classification, as commonly practised. It depends upon the 
recognition not of one character or of two, arbitrarily selected as suitable 
for ready use : but of as many characters as possible, which shall collectively 
serve as criteria for comparison. In respect of each of these, variation will 
be found as we pass from type to type. Such variations must be seriated, 
and it will usually appear that they fall between two extremes. The question 
then arises of the relative age of these extreme types. They may, of course, 
have resulted from divergence from some middle type, and the enquirer 
