i'Ki:sii)i:xi'i.\r. addkkss — siaTiox w. 



39 



To the north-west He masses of grit, and their western Hmit 

 forms a gr^at escarpment overlooking the Congo basin. Jt thus 

 leads to the extension of the continental area much further west 

 than anticipated. It repeats in a remarkable way the rift faults 

 and depressions of India and East Africa, and suggests some 

 explanation of the low-lying Congo basin and its connection with 

 I'razil. 



The Pro]5lem of the Flora. 



As the remarkable nature of the fossil flora of the period 

 under criticism was the means of arriving at a correlation of 

 the strata of such distant parts of the world, and as its distribu- 

 tion suggests problems of ancient geography that yet require 

 elucidation, it is advisable to ofl'er a short description of the 

 CJossopfcris flora of Gondwanaland. From Mr. Newell Arber's 

 work* I extract somewhat freely. 



The early primary formations of the world show no fossil 

 plant remains — probably on account of the minuteness and 

 fragile nature of the first forms of vegetation, and also owing 

 to the alteration of the enclosing sediments. In Silurian age 

 occur the earliest known fossil plants, which were the precursors 

 of the Devonian and Lower Carboniferous flora, the latter 

 characterised by remarkable uniformity throughout the W'Orld. 

 even including some of the regions that subsequently developed 

 Clossof^fcn's. 



In the succeeding Permo-Carboniferous deposits are found 

 l^lant remains that belong to another vegetable epoch, yet divided 

 into two well-marked botanical provinces, one existing in 

 Europe, North America, and North Asia contemporaneously 

 with a dissimilar type confined for the most part to India and the 

 parts of the Southern Hemisphere already alluded to, Australia, 

 South America, South, and we may now add Central, Africa. 



" The flora of this province differed remarkably from that of the 

 northern province, and it is now g-enerally accepted that these two 

 types of Permo-Carboniferous vegetation flourished on two great conti- 

 nental regions for the most part, Init not entirely- isolated and widely 

 separated from each other." t 



The Gondwanaland plants are characterised by the frequent 

 occurrence of Glossol^tcris — a fern-like plant from which the 

 flora takes its name. 



The Lower Carboniferous and Devonian flora consisted of 

 the representatives of six great groups — Equisetales (including 

 Horsetails, and Calamites) and Lycopods (with the club mosses, 

 Sigillaria. etc.), the Sphenophyllales and Cordaitales. both of 

 which have been long extinct, and the fern-like plants Filicales 

 (true ferns') and Pteridospermse, which are numerous. 



In Copper Carboniferous and Permian times the same six 

 groups were still dominant, whether in the north or south con- 

 tinents, but three nevv groups made their first appearance — viz., 



* ■ The Glossoptcris Flora," British Museum Catalogue : E- A- Newell 

 Ar1)er. 1905. 



t Xewell Arber. op- cii-. p- xvii- 



