PREFACE. 
Yll 
sun, and the result observed with a magnifier, the bursting 
of the capsules and the dispersion of the spores , or seed- 
buds, may be seen to great advantage. The sori, or bundles 
of capsules, are sometimes elevated upon a flat or saucer- 
shaped receptacle ; and sometimes arranged round a stalk, 
or sunk in a cyst, as in Dansea : rarely, the capsules lie 
solitary, or in pairs, upon the frond itself. The sporangia 
may be observed covered with a membrane, called an 
indusium , or involucre , or they are naked. From these 
characters, and from the form, arrangement, absence, or 
presence of them, Ferns are divided into tribes, genera, 
and species. Species are the distinct forms belong- 
ing to one genus ; genera are the distinct groups of 
species belonging to one tribe. Species may be further 
divided into varieties ; the Hart's-Tongue, Scolopendrium 
vulgar e, for example, has no less than between three and 
four hundred marked variations from the simple or normal 
form, catalogued by cultivators of the species.* 
Collectors of Ferns, whose knowledge of the primary 
characters of a species has been confined to the study of a few 
fronds, gathered perhaps in one, and that a limited locality, 
are often tempted to assume unusual deviations from the 
primary characters, as proofs of a distinct species : and by 
this means, the names of Ferns have been greatly and 
inconveniently multiplied. There is no necessity to give a 
name to every variety of form : the true botanist can wait 
for more exact and comprehensive acquaintance with 
characters which do, and do not, distinguish species : and 
when, by experience, he is able to determine such marks, 
imaginary species fall back into the rank of varieties ; or he 
is able, with the confidence of accurate observation, to pro- 
nounce that a true species, which by others may have been 
incorrectly regarded as a variety of some other form. 
The popular taste for plants of this class has brought 
* See List of British Ferns and their Varieties, compiled by P. Neill Fraser, 
Esq., Edinburgh, 18 G 8 . 
