Sigillaria Sentence Examples
In erratic blocks of sandstone, found on the Disco shore of the Waigat, have been detected a Sigillaria and a species of either Pecopterisor Gleichenia, perhaps of this age; and probably much of the extreme northern coast of Ellesmere Land, and therefore, in all likelihood, the opposite Greenland shore, contains a clearly developed Carboniferous Limestone fauna, identical with that so widely distributed over the North American continent, and referable also to British and Spitsbergen species.
These include among others, Glossopteris browniana, Gangamopteris cyclopteroides, Sigillaria Brardi, Bothrodendron Leslii, Noeggerathiopsis Hislopi.
The Carboniferous forerunners of the tiny club-moss were then great trees with dichotomously branching stems and crowded linear leaves, such as Lepidodendron (with its fruit cone called Lepidostrobus), Halonia, Lepidophloios and Sigillaria, the largest plants of the period, with trunks sometimes 5 ft.
This order includes only, extinct forms, the best known of which are the plants placed in the genera Lepidodendron and Sigillaria.
In Sigillaria the latter form vertical rows, while in Lepidodendron the arrangement is a complicated spiral.
In the case of incrustation the whole substance of the fossilized specimen - e.g., a stem of Sigillaria - may be replaced by mineral matter, such as sandstone or shale, giving a cast of the whole, on the outer surface of which the external markings, such as the bases of leaves and the scars left by their fall, are visible in their natural form.
Thus the roots of Sigillaria are called Stigmaria, detached leaves Sigillariophyllum, and the fructifications Sigillariostrobus; the name Sigillaria applies to the stem, which, however, when old and partly decorticated has been called Syringodendron, while its woody cylinder has often been described under the name Diploxylon.
For example, the form and structure of Stigmaria have long been well known; but it is seldom possible to determine whether a given Stigmaria belonged to Sigillaria, Lepidodendron or some other genus.
We will first take the arborescent Lycopods, as in every respect the more important group. They may all be classed under the one family Lepidodendreae, which is here taken to include Sigillaria.
To these, underground organs the name Stigmaria is applied; they are not clearly distinguishable from the corresponding parts of Sigillaria.Advertisement
The usually crowded leaf-cushions are spirally arranged, and present no obvious orthostichies, thus differing from those of Sigillaria.
The chief distinctive character of Sigillaria lies in the arrangement of the leaf-scars, which form conspicuous vertical series on the surface of the stem.
The anatomy of Sigillaria is not so well known as that of Lepidodendron, for specimens showing structure are comparatively rare, a fact which may be correlated with the infrequency of branching in the genus.
On the whole, the anatomy of Sigillaria is closely related to that of the preceding group, and in fact a continuous series can be traced from the anatomically simplest species of Lepidodendron to the most modified Sigillariae.
The nature of the fructification of Sigillaria was first satisfactorily determined in 1884 by Zeiller, who found the characteristic Sigillarian leaf-scars on the peduncles of certain large strobili (Sigillariostrobus).Advertisement
The discovery of Sigillariostrobus, which was the fructification of Subsigillariae as well as of the ribbed species, has finally determined the question of the affinities of the genus, once keenly discussed; Sigillaria is now clearly proved to have been a genus of heterosporous Lycopods, with the closest affinities to Lepidodendron.
These organs, to which the name Stigmaria was given by Brongniart, have been found in connexion with the upright stems both of Sigillaria and Lepidodendron.
It has been maintained by some palaeobotanists that the aerial stems of Sigillaria arose as buds on a creeping rhizome, but the evidence for this conclusion is as yet unconvincing.
The genera Lepidodendron, Sigillaria, Stigmaria, or Calamites, which played so great a share in the vegetation of the same age in the northern hemisphere, have not been recognized among the Palaeozoic forms of India, but examples of Sigillaria, Lepidodendron and Bothrodendron are known to have existed in South Africa in the Permo-Carboniferous era.
A similar association was found also in Argentine rocks by Kurtz (Map A, G1), and from South Africa Sigillaria Brardi, Psygmophyllum, Bothrodendron and other northern types are recorded in company with Glossopteris, Glangamopteris and Naeggerathiopsis.Advertisement
Among plants from Lower Triassic strata there are a few which form connecting links with the older Permo-Carboniferous flora; of these we have a species, described by Blanckenhon as Sigillaria oculina, which may be correctly referred to that genus, although an inspection of a plaster-cast of the type-specimen in the Berlin Bergakademie left some doubt as to the sufficiency of the evidence for adopting the generic name Sigillaria.
Another Triassic genus, Pleuromeia, is of interest as exhibiting, on the one hand, a striking resemblance to the recent genus Isoetes, from which it differs in its much larger stem, and on the other as agreeing fairly closely with the Palaeozoic genera Lepidodendron and Sigillaria.
Arborescent Pteridophytes are barely represented, and such dominant types as Lepidodendron, Sigillaria, Calamites and Sphenophyllum have practically ceased to exist; Cycads and Conifers have assumed the leading role, and the still luxuriant fern vegetation has put on a different aspect.