Explanatory. 
when the pinnae have distinct leaflets these are pinnules : 
segments and lobes are terms indifferently applied to the projecting 
parts of notched fronds, pinnae, and pinnules ; the recess between 
lobes is a sinus. A frond is pinnate when its pinnae are quite 
separate from each other ; when they unite before reaching the 
rachis : the frond is pinnatijid ; bi-tri-pinnate and bi-tri-pinnatijid 
are terms applied to fronds which are thus divided twice or thrice, 
their pinnae and pinnules being more or less deeply cut in like 
manner with the frond itself : when a frond has neither pinnae nor 
pinnules itis simple. Each of the little masses of fructification* 
is a sorus, and generally consists of a number of capsules which 
in their turn contain spores — the microscopic reproductive organs. 
The capsules are sometimes surrounded wholly or in part by an 
elastic ring or annulus , a microscopic feature in most ferns ; but 
in others, especially in some of the tree-ferns, distinctly visible 
with the aid of a pocket lens, and bearing the appearance of a 
spiral wire spring of exceeding fineness and beauty. In some 
species the capsules are placed on a receptacle elevated from the 
surface of the frond, and they have also in many cases a covering 
which varies in form and substance, and is called an involucre § 
when this is wanting the sorus is said to be naked. By means 
of the growth, arrangement, and absence or presence, of these 
different parts, the order Filices has been divided into tribes , 
genera and species : a gradually narrowing circle, one tribe often 
Containing many genera ; each genus, many species ; and great 
[variation even being sometimes observable between individuals of 
a species. To this last point we would particularly draw the atten- 
tion of our readers : each species is generally supposed, (although 
.there is great difference of opinion upon the subject,) to have pro- 
ceeded from its own parent plant, but often, from difference of 
climate, soil, or situation, individuals of a species vary consider- 
ably ; so that when ferns, although apparently very different, are 
apt to revert to one original type ; or when specimens have been 
found which by a series of extremely close links unite each other 
to some particular species, they are only considered vai'ieties as 
they may well be referred to a common parent plant. Many 
Perns varying in this way have received names as new species ; and 
me only partially acquainted with botany is very apt to make 
:his mistake, as the varieties which complete the chain are often 
Pound in far distant localities. Thus, Dr. Hooker observes, that 
before he could define the characteristics of Lomaria procera , 
‘whose varieties to an unpractised eye are more dissimilar than 
)ther species of the same genus,” he had to examine many hundred 
specimens of that plant gathered not only in New Zealand, but in 
Australia, South Africa, and South America. 
* Or seeds. 
§ It should be observed that the invobucra often fall off or are hidden 
vhen the fructification is very fully developed so that specimens with 
mmature as well as mature sori should be examined. 
o 
