Recent years, of Zeiller in France, and Scott, Seward and others in England, has advanced our knowledge of the anatomy of ~fossil plants in an important degree.
In cases of doubt, evidence may be obtained from traces of organic structure, from the presence of carbonaceous matter, or, as Zeiller has pointed out, by the remains of animals such as Bryozoa being attached to the cast, showing that it represents a solid body and not a mere cavity or furrow.
On the whole, it cannot be said that the Palaeozoic remains have as yet thrown much light on the evolution of the Algae, though we may not be prepared to maintain, with Zeiller, that plants of this class appear never to have assumed a form very different from that which they present at the present day.
In one or two cases Palaeozoic plants, resembling the true Mosses in habit, have been discovered; the best example is the Muscites polytrichaceus of Renault and Zeiller, from the Coal Measures of Commentry.
Williamson thoroughly worked out, in petrified specimens, the organization of a cone which he named Bowmanites Dawsoni; it was subsequently demonstrated by Zeiller that this fructification belonged to a Sphenophyllum, the cones of the well known species S.
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).
Or more in diameter) were found lying loose on the sporophylls by Zeiller; the sporangia containing them were first observed by Kidston, in a species from the Coal Measures of Yorkshire.
The genus Selaginellites, Zeiller, is now used to include those forms in which the fructification has proved to be heterosporous.
Genus, ranging throughout the Carboniferous, the elongated sporangia individually resemble those of Marattiaceae, but they are completely isolated, the characteristic grouping in sori being absent; the same remark applies to the Sphenopteroid Renaultia of Zeiller (fig.
(1910); Solms-Laubach, Introduction to Fossil Botany (Oxford, 1892); Zeiller, Elements de paleobotanique (Paris, 1900).
Phyllotheca has been recognized in Europe in strata of Palaeozoic age, and Professor Zeiller has discovered a new species - P. Rallii- in Upper Carboniferous rocks in Asia Minor (Map A, VII.), which points to a close agreement between this genus and the well-known Palaeozoic Annularia.
Phyllotheca occurs also in Jurassic rocks in Italy and in Siberian strata originally described as Jurassic, but which Zeiller has shown are no doubt of Permian age.
In 1895 Professor Zeiller described several plants from the province of Rio Grande do Sul in South America (Map A, including a few typical members of the Glossopteris flora associated with a European species, Lepidophloios laricinus, one of the characteristic types of the Coal period, and with certain ferns resembling some species from European Permian rocks.
By Professor Zeiller - and this author has recently made important additions to his original account - which demonstrates an admixture of Glossopteris types with others which were recognized as identical with plants characteristic of Rhaetic (After Feistmantel.) FIG.
A few plants described by Potonie from German and Portuguese East Africa demonstrate the occurrence of Glossopteris and a few other genera, referred to a Permo-Triassic horizon, in a region slightly to the north of Tete in the Zambesi district (Map A, I.), where typical European plants agreeing with Upper Carboniferous types were discovered several years ago, and described by Zeiller in 1882 and 1901.
(1896); Zeiller, Elements de paleoboiansque (Paris, 1900); Potonie, " Fossile Pflanzen aus deutsch and portugiesisch Ostafrika," Deutsch-Ostafrika, vii.
1910, with bibliography; Zeiller, " Revue des travaux de paleontologie vegetale," Rev. gen.
The Mount Vernon beds, which occur about the middle of the series, have as yet yielded only a small number of species, though these include the most interesting early Angiosperms. Among them are recorded a Casuarina, a leaf of Sagittaria (which however, as observed by Zeiller, may belong to Smilax), two species of poplar-like leaves with remarkably cordate bases, Menispermites (possibly a water-lily) and Celastrophyllum (perhaps allied to Celastrus).