Palaeontologie. 285 



break in the succession of Northern floras, which is not apparent 

 between the Permian and Triassic floras of the Sonth. 



A comparative view of the plants, found in various parts 

 of the world, in beds ranging from the upper Trias to the top 

 of the Jurassic System, reveals a striking uniformity in the 

 Vegetation both in Northern and Southern latitudes during this 

 long succession of ages. The Palaeozoic types are barely 

 represented, the arborescent Vascular Cryptogams have been 

 replaced by Cycads, Ginkgoales, and Conifers, while Ferns con- 

 tinue to hold their own. No undoubted Angiosperms occur in 

 the rocks of this period. 



The Author next passes in review the different classes of 

 plants, which constitute the flora of the Jurassic and Wealden 

 periods. Among Algae, attention is called to the presence of 

 the Charophyta, the earliest known Diatoms, and the 

 calcareous Siphoneae. The Bryophyta are apparently as poorly 

 represented as in the Palaeozoic rocks, and it is hardly too 

 much to say that no absolutely trustworthy examples of Mosses 

 have so far been found in Mesozoic strata. 



The Mesozoic members of the genus Equisetites, which 

 replace the Palaeozoic Calamites, differ, as far as we know, in 

 no essential respect from existing Equisetums. Of Mesozoic 

 representatives of the Lycopodiales there are, however, practi- 

 cally none of botanical interest, except Sigillaria oculina and 

 Plearomeia. 



Among the Mesozoic Filicales, many fern-like plants are 

 known only from sterile fronds, and in some cases it is difficult 

 to say whether these should not be more properly relegated to 

 the Cycads than to Ferns; a difficulty which is a necessary 

 consequence of the common origin of these two classes. There is 

 also some reason to believe that synthetic types, combining the 

 characters of both Ferns and Cycads, persisted into the Mesozoic 

 period, e. g., Otozamites. Marattiaceous ferns are, in marked 

 contrast to the Palaeozoic period, scarce in Mesozoic rocks, and 

 of the Ophioglossaceae, there are no satisfactory examples. It 

 would appear that the Eusporangiate Ferns suddenly sank to 

 a very subordinate position after the Palaeozoic area. 



Osmundaceae are however more prominent, and the 

 Schizaeaceae and Gleicheniaceae are also well represented. The 

 recent genera Matonia and Dipteris are survivals of numerously 

 represented fern types in the Mesozoic rocks. A map showing 

 the past and present distribution of Matonineae and Dipteridinae 

 is given. The Cyatheaceae were also much in evidence at this 

 period, but among the Mesozoic ferns, there are comparatively 

 few that can with good reason be referred to the Polypodiaceae. 



The abundance of Cycadean plants is one of the most 

 striking features of the Mesozoic floras, and some of the nume- 

 rous types of fronds are briefly described. The most striking 

 fact in the distribution of Mesozoic Cycads is the occurence of 

 abundance of such plants in the Mesozoic rocks of India, 



