836 REPORT— 1903. 



a development in northern latitudes. There is, moreover, another consideration, 

 and that is the eifect on the vegetation of an enormous continental mass ; in North 

 America and Europe it is probable that the forests grew on low-lying land pene- 

 trated by lagoons and in part submerged under shallow brackish water, a disposi- 

 tion of land and sea very different from that in the so-called Gondwana Land of 

 the South. Possibly the apparently uniform vegetation of the Devonian and 

 Lower Carboniferous period was unable, through stress of climatal conditions, to 

 prolong its existence in the southern area, while in the north it continued to 

 flourish, and as the evolution of new types proceeded in rapid succession it was 

 not slow to colonise new areas stretching in South America and South Africa to 

 the confines of the Glossopteris flora. 



There seems good reason for assuming that the Glossopteris flora originated in 

 the South and before the close of the Permian period, as well as in the succeeding 

 Triassic era, pushed northward over a portion of the area previously occupied by 

 the northern flora. This northward extension is shown by the existence of 

 Glossopteris in Upper Permian rocks of Russia, by the occurrence of several southern 

 types in plant-bearing beds of the Altai mountains, and by the existence in Western 

 Europe during the early stages of the Triassic era of such southern genera as 

 A'europteridiwn and Schizoneuia, 



Triassic, Jurassic, and Wealden Floras. 



It is unfortunate that the records of plant-life towards the close of the 

 Palaeozoic and during the succeeding Triassic period are very fragmentary ; the 

 documents are few in number, and instead of the fairly continuous chapters in 

 which the records of the Coal age have been preserved, we have to be content 

 with a few blurred pages. During the Triassic period the vegetation of the world 

 gradually changed its character ; the balance of power was shifted from the 

 Vascular Cryptogams, the dominant group of the Palaeozoic era, to the Gymno- 

 sperms. It is not until we pass up the geologic series as far as the Ehsetic 

 formation, that we come to palaeobotanical records at all comparable in their 

 completeness with those of the Permo-Carboniferous era ; but before considering 

 the Rhsetic vegetation we must glance at such scattered relics as remain of the 

 vegetation belonging to the period of transition between the Palaeozoic and 

 Mesozoic facies. It is regrettable that this transitional period is unusually poor 

 in documentary evidence that might throw light on the gradual change in the 

 facies of Palaeozoic vegetation. The new order, when once established, persisted 

 for many succeeding ages without undergoing any essential alteration. 



One of the few floras of early Triassic age of which satisfactory relics have been 

 preserved is that described in 1844 by Schimper and Mougeot from the Bunter 

 Sandstones of the Vosges. The genus Neuropteridium, a plant which may be a 

 true fern, or possibly a surviving member of the Cycadofilices, is represented by a 

 species which can hardly be distinguished from that which flourished in South 

 America, South Africa, and India in the Permo-Carboniferous period. This 

 genus and another southern type, Schizoiieura, both of which are met with in the 

 Triassic rocks of the Vosges, would seem to point to a northern migration of 

 certain members of the Glossopteris flora, which took place at the close of the 

 Paleozoic era. In the Lower Triassic flora Conifers are relatively more abundant 

 than in the earlier periods ; such genera as Albertia (resembling in its vegetative 

 features some recent species of Araucaria), Voltzia (with cones that cannot be 

 closely matched with those of any existing members of the Coniferae), and other 

 representatives of this class are common fossils. Lepidodendra have apparently 

 ceased to exist; Sigillaria may be said to survive in one somewhat doubtful form, 

 iSiyillaria oculina. The genus Pleuromeia, which makes its appearance in Triassic 

 rocks, is known only in the form of casts exhibiting a strong likeness to some 

 Palaeozoic Lycopods, and is perhaps more akin to Isoetes than to any other exist- 

 ing plant. The Calamites are now replaced by large Equisetaceous plants, which 

 are best described as Horsetails with much thicker stems than those of their 

 modern descendants. 



From Recoaro in Northern Italy some of the Vosges genera have been recorded, 

 and a few other European localities have furnished similar relics of a Triassic 



