370 
THE FLORIST. 
FERN CLASSIFICATION.—No. III. 
Before proceeding to show how the principal group of the Polypo- 
piaceoe —the Polypodineoe, are divided into subordinate groups, it will 
be necessary to enter on an explanation of the peculiarities of structure, 
and of the terms representing them, which are employed for this 
purpose. 
The veins of the fronds (Venation) and the sori (Fructification) 
are the parts of the plant which are mainly resorted to in effecting the 
subdivision of the Polypodinece into groups of lesser value. There are 
various plans upon which the characteristics afforded by the differences 
to be found in these organs have been applied, producing differences in 
the extent and nature of the resulting groups. The plan which we 
prefer, as neither combining too great differences of structure nor sub¬ 
dividing to an unnecessary extent, consequently admitting of the most 
satisfactory definitions, is that which we have proposed in the “ Index 
Filicum,” and which will be adopted here. 
The veins are the ribs or fibres which traverse the fronds, and serve 
to give them their form and elasticity. They form the framework of 
the plant, on which the herbaceous portions are, as it were, spread out 
to the influences of light and air, as occurs in the leaves of phseno- 
gamous plants. They consist of bundles of woody fibre traversed by 
the nourishing vessels, and are hence sometimes spoken of as consti¬ 
tuting the vascular system of the plant. 
In the Stipes or stalk of the frond, the main part is constituted of the 
vascular and woody tissues, which are arranged in definite bundles or 
plates tolerably uniform in character in closely related plants. The 
arrangement of these has been applied to the purposes of classification, 
though without much success. These firmer tissues of the stipes are 
sometimes continuous at the base with those of the caudex, so that the 
fronds do not separate spontaneously, and in such cases the fronds are 
said to be adherent to the stem ; but in other species there is, at or near 
the base of the stipes, a natural articulation or joining, so that, when its 
functions cease, the frond separates and falls away, leaving a clean scar 
on the rhizome or caudex, and where this happens, the fronds are said 
to be articulated with the stem. 
Commencing, then, with the stalk or stipes, we find this system of 
vessels and woody fibre continued onwards throughout the lamina or 
leafy part of the frond, and branching more or less according as the 
frond itself is more or less divided, forming, as the case may be, rachis, 
costa, or one of the various gradations of veins, up to the smallest veinlet. 
When the frond is simple, that is undivided, as in the common Hart’s- 
tongue, the continuation of vascular and woody tissue, from the stipes 
through the frond, forms the Costa or midrib. From this costa may be 
given off, laterally, branches of more slender proportions, of which the 
first series are the Veins ; the next, branching out from these the Venules ; 
while the third series where they occur, and all beyond them, are called 
Veinlets; the last series, when the venation is very compound, being 
distinguished as the ultimate veinlets. If the frond is divided into 
separate leaflets, or Pinnce as they are collectively called, as, for instance, 
