452 Ill. SEGREGATES AND 
ferns treated separately on pages 411—2, under the specific 
names of spinulosa, dilatata, and @mula. The most dissimilar 
views still hold place among our botanical authorities in respect to 
the specific relationships of these ferns. They had, however, been 
described as distinct species so frequently, with so many special 
localities recorded for each, that it was found practicable to treat 
their distribution apart on preceding pages. Such was the rule 
followed in all cases where it was found at all possible to act up to 
it. But those botanists who have looked over the examples of 
name-confusion given on preceding pages, will hardly experience 
difficulty in believing that the rule must have proved an 
impossible one in some instances. 
Ferns appear to have been understood very imperfectly by the 
ante-Linnean botanists; and even through the books of the 
eighteenth century there runs a want of clear distinctions between 
them. Perhaps some Fern-lovers will be ready to declare, that 
such want of clearness is still to be found in the writings of 
leading botanical authorities even past the middle of the nine- 
teenth century. This want of clear perception about them may be 
attributed mainly to the examination of dried fronds in the 
herbarium, more than a careful observation of the whole living 
plants in the wilds, or even under less natural conditions in the 
gardens. Several of the allied species are so closely similar 
during the first few years of their existence, that single fronds of 
them in the herbarium can scarcely be distinguished, unless by 
those botanists who have become specially familiar with the 
several species as they appear at their different ages. In this 
respect they may be likened to shells, many species of which 
must be traced from young age to mature growth, through 
series of specimens, before they can be understood sufficiently. 
The manner of growth or evolution, the kind of rootstock or 
rhizome, so seldom shewn by herbarium specimens of ferns, will 
occasionally serve well to decide a question about difference, 
which fronds alone in the herbarium would leave unsolved. 
An instance of this sort of assistance will not be unuseful, 
and here scarcely out of place, because it throws light on the 
