Picture - Cosmic Polymath

RESEMBLANCES BETWEEN WINGED SEEDS AND REAL WINGS 421
PLATE XOVI {continued)
wing is triangular in shape, concavo-convex, and elastic throughout. It tapers from the root towards the tip, and from the
anterior towards the posterior margin. It is thickest, strongest, and most rigid at the root and along the anterior margin (a),
and thinnest, weakest, and most elastic along the posterior margin (h). It presents a continuous membrane to the air during
both the up and down strokes, as in the insect ; it, however, partially closes or folds during the up stroke and fully expands during
the down stroke, as in the bird. The wing consists of muscles, bones, and a continuous elastic membrane which is supported by
the bones of the arm, fore-arm, and hand, and by the bones of the thigh, leg, and tail. It is a most elegantly constructed,
serviceable wing; the bats being splendid flyers. Drawn for the present work by 0. Berjeau, from a specimen in the Author's
collection.
Fig. 6.—The humming-bird {Amaxilia fuscocaudaia). Displays a most dainty, exquisitely-formed, concavo-convex wing, composed
of bones, muscles, and feathers, the latter radiating in an outward and backward direction. The feathers which take part
in flight are divided into primary or rowing feathers (tip of wing), secondaries (middle portion of wing), and tertiaries (root of
wing). The wing resembles in all respects that of the insect, with this difference, that the primary, secondary, and tertiary
feathers open up and separate during flexion and the up stroke, and close during extension and the down stroke. The wing of
the insect, and also that of the bat, presents a continuous, unbroken surface during both the up and down strokes, a. Semi-rigid
anterior margin tapering from root to tip of wing ; h, posterior, thin, elastic, yielding margin of wing formed by the free ends of
the primary, secondary, and tertiary feathers. Drawn for the present w ork by C. Berjeau from a specimen in the Author's private
collection.
Fie. 7.—The cicada (Cicada septemdecim). This is one of the best flying insects ; its body being compact and finely formed, and
its wings, which are four in number, being ample, long, and somewhat narrow. The body and wings are carefully adapted to each
other, and the spectator is impressed with the idea of fitness in the general arrangements. The wings are beautifully transparent,
and the venation nervures or supports of the wings radiate in an outward and backward direction, and are connected by transverse
nervures which produce an open network. The nervures forming the anterior margins of the front wings are finely graduated,
and taper from the root in the direction of the tips of the wings. The wings of thecicada may be regarded as typical wing structures.
It is a curious circumstance that the winged seed of the plane-tree greatly resembles them, both as regards general
contour and venation. Drawn for the present work by 0. Berjeau, from a specimen in the Author's collection.
Fig. 8.—The red-legged partridge {Perdrix ritbra), with the wings fully extended as in rapid flight. Shows the deeply concave
form of the wings, how the primary and secondary feathers overlap and support each other during extension, and how the anterior
or thick margins of the wings are directed upwards as in the kite. The wings in the partridge are wielded with immense velocity
and power, and this is necessary because of their small size when compared with the great size and « eight of the body. From a
photograph taken by the Author in 1867, and drawn with great care by C. Berjeau during the same year.
It may appear far-fetched, but there is a more or less direct connection between the distribution of seeds and
the migration of animals, especially of birds. This connection is most perceptible in the case of well-formed winged
seeds, and such as are furnished with appliances which permit the wind to lay hold of them when falling and to
carry them to considerable distances from where they were originally grown. Nature has provided quite a large
number of plants with a distinct mode of dissemination.
The most outstanding examples of winged seeds, as indicated, are provided by the ash-tree and plane-tree, both
of which structurally greatly resemble certain wings. Thus the seed of the ash is twisted upon itself in the direc-
tion of its length, propeller-fashion ; while the seed of the plane-tree is scarcely distinguishable from any of the
volant wings.
The seeds of the ash and plane-tree, especially the latter, reveal a most unlooked-for resemblance between wings
which are intended to vibrate and sustain volant animals in the air, and wings which are not intended to flutter,
but only to act as parachutes and delay the rapidity of the fall of the flying bodies. In the one case, the flight is
active and is due to inherent muscular powers ; in the other, it is passive and is traceable to the action of the wind
—this causing the winged seeds to gyrate in their descent and to be carried, in some instances, long distances before
they reach the ground.
The resemblances between winged seeds and real wings afford another outstanding example of type, and
design as revealed by type, which is everywhere met with in the organic kingdom. Type, which in one sense is
another name for general plan, while it finds its most striking examples in the organic kingdom, is not confined to
that kingdom. On the contrary, it goes further and deeper. It includes the inorganic kingdom also. This is
seen in the structure of crystals, dendrites, basaltic rocks, &c. In the organic kingdom the types or examples of
a general plan are increased in number, but they all tell the same tale, namely, the story of premeditation
and design.
The winged seeds are to be regarded as the homologues or precursors of true wings.
As indicating the persistence of type or general plan it should be stated that there were wing structures in early
geologic times, and that several of the extinct reptiles (Pterodactyls) flew, as proved by their fossil remains. The
winged type of structures is very ancient, and the fact that it has persisted to the present day shows very clearly
that it is no chance product, but rather a part, and a leading part, of the great subject of locomotion, on which the
majority of animals, and not a few plants, depend for their food-supply.