26 
THE FERN WORLD 
constant distinctions, these constitute what are called varieties. 
Ascending, however, from the collections of individuals 
which we range under species, we come to what is called a 
genus — a term which includes one or more — generally more 
than one — species. A collection of species having certain 
marked and important points in their structure in common 
constitutes a genus, and an assemblage of genera, differing in 
many respects from each other, but still having certain features 
in common, constitutes an order. By such a method ol 
arrangement or classification we are enabled to group the 
inhabitants of the Fern world, and exhibit the relationship 
which exists between them. 
It will now be interesting to inquire what are the points 
of resemblance or of disagreement which suggest the inclu- 
sion or the exclusion of certain forms of Fern life under or 
from particular orders or groups. Before the time of the 
great Swedish naturalist, Linnaeus, a rude and imperfect 
system of classifying plants had been adopted. The rougher 
features of Ferns, for instance, were selected in order to 
facilitate and guide systems of classifying them. When it 
was found that there were points of resemblance in the 
general appearance of the fronds and in the habits of the 
plants, the fact was considered sufficient to warrant their 
classification in groups, marked by these general or rough 
characterizations. 
Linnaeus, however, and those who followed him, invented 
and perfected between them a system of classifying Ferns 
in accordance with the points of resemblance suggested 
by the shape and position in the several species of the 
seed clusters, which in general pass under the name of 
fructification. As the fructification of Ferns takes place 
upon some part — either in the middle or at the ends — 
of the veins which intersect the leafy substance of the fronds, 
the particular character of the veining of the fronds has 
