When finely reticulated they might be mistaken for the venation of leaves, and, when complicated with little rill-marks tributary to their sides, they precisely resemble the Dictyolites of Hall from the Medina sandstone (Fig.
Fleming found an organism which in form somewhat resembles the spike of one of the grasses, save that the better preserved bracts terminate in fan or kidney-shaped leaflets, with a simple venation radiating from the base.
The simple rectilinear venation of ribbon-like fronds, usually much broken, that occurs in the Lower Old Red Sandstone, has often reminded me of that exhibited by this exotic species of Zostera.
But it has since been assigned to a greatly lower order,--the ferns; and Sir Charles Lyell has kindly shown me that an exotic fern of the present day exhibits exactly such a reticulated style of venation as my Helmsdale fragment.
The venationis not distinctly preserved; but enough remains to show that it must have been peculiar,--apparently radiating outwards from a series of centres ranged along the midrib.
The larger resemble a Tæniopteris of the English and Continental Oolites, save that its midrib is more massive, its venation less at right angles with the stem, its base more elongated, and its size much greater.
The leaves of Monocotyledons have generally this kind of venation, while reticulated venation most usually occurs amongst Dicotyledons.
The leaf in this case is multicostate and thevenation palmate.
The divisions of leaves with radiating venation may extend to near the base of the leaf, and the names bipartite, tripartite, quinquepartite, &c.
To a distribution of veins such as this the name of reticulated or netted venation has been applied.
A leaf with only a single midrib is said to be unicostate and the venation is described as pinnate or feather-veined.
The union of the parts may be complete, and the calyx may be quite entire or truncate, as in some Correas, the venation being the chief indication of the different parts.
The venation is useful as pointing out the number of leaves which constitute a gamosepalous calyx.
On account of the venation Presl referred this plant to his section Arthrobotrys.
I have not seen the specimens, but, as similar venation and not very dissimilar fronds are seen in Woodwardia and Pteris, one may perhaps doubt the absolute certainty of the identification.
The venation is free, and the sori are dorsal on the veins.
The venationis peculiar, and the disposition of the sori depends mainly on the peculiarities of the venation.
Under normal circumstances it will be found that laminar venation is most common in gamosepalous and vaginal venation in polysepalous calyces.
In Primula or Pedicularis, where the venationis clearly laminar, the tubular portion is distinctly calycine.
It is not in all cases easy to trace the origin and true nature of the ascidium, as the venation is sometimes obscure.
This is distinguished from all the other sub-genera of the old genus Vanessa by a small difference in the venation of the wings (the discoidal cell of the hind-wings is open instead of closed).
Not only is the moth-like appearance characteristic, but the venation of the wings (fig.
The wing venationand mouth-parts are shown in figures 77 and 78.
It is related to Culicoides but differs in the number of antennal segments and in its wing venation (fig.
The venation is simpler than in the mosquitoes and the veins are usually less distinct.
Some years ago we used the following method for studying the venation of the wings of small Lepidoptera.
The balsam mount is also unsatisfactory in many respects, as the body is always more or less distorted and little can be relied upon except the venation and the jointed appendages.
The student of Lepidoptera will frequently find it necessary in the study of the venation of wings to bleach them or denude them of their scales in some way.
Make drawing showing venation in the butterfly's wings.
The venation of insects' wings is much used in insect classification, and the various veins have been given names.
The venation is strictly parallel, the midrib usually strong, and the other ribs more slender.
In Anomochloa there are several nearly equal ribs and in some broad-leaved grasses (Bambuseae, Pharus, Leptaspis) the venation becomes tesselated by transverse connecting veins.
The most authoritative classifications of butterfly families are based upon the peculiarities of wing venation and are admirably discussed in such books as Holland's "Butterfly Book" and Comstock's "How to Know the Butterflies.
Aside from certain peculiarities of the wing-venation (a costal and a humeral vein on the hind wings) these Metal-marks may be known by their minuteness and the bright metallic markings on the brown wings.
The venation is parallel from base to apex in nearly all our grasses, but such is not always the case--e.
He shows in a very convincing manner that the whole diversity of leaf venation can be understood from these three principles.
Even the venationof leaves, which was formerly considered to be entirely without significance, has been shown to possess a high biological value by the ingenious investigations of J.
He shows that the venation of a leaf is in every case exactly adapted for the fulfilment of its purpose.
Characterized by the fern-like venation of the pinnae, which have a prominent midrib, giving off at a wide angle simple or forked and occasionally anastomosing lateral veins.
The shape of the calyx, which is generally present on unhulled seed, and the venation of the seed pods also distinguish it.
The venation and shape of the seed pods are important characters in distinguishing the different species of sweet clover.
One is a species of Didymosorus, and shows distinct venation and fructification.
In the same fern we meet also with different kinds of venation in the fronds.
Characters taken from the venationand forms of the fronds are not always to be depended upon, if we are to judge from the Ferns of the present day.
But with care the leaves can be spread open, and their shape and venation seen.
Thick and dark green, with plain margins, and conspicuously looped venation near the edges, these leaves suggest a young magnolia tree.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "venation" in a variety of sentences. We hope that you will now be able to make sentences using this word. Other words: artery; capillary; vein
