May 18, 1906.] 



SCIENCE. 



781 



glomerate of South Africa, the glacial de- 

 posits of New South Wales, Queensland and 

 Tasmania, of the Salt range of India and of 

 Brazil) is usually known as the Glossopteris 

 flora, so-called by Neumayr because of the ex- 

 treme abundance of the undivided fronds of 

 this fern-like plant. This flora is assumed 

 to have been more or less completely isolated 

 from the continental mass of the northern 

 hemisphere, and to have flourished over a 

 great southern continent termed by Suess 

 Gondwanaland from the typical Glossopteris- 

 bearing rocks of the lower part of the lacus- 

 trine Gondwana system of India. 



This Glossopteris flora may be roughly char- 

 acterized and contrasted with that which 

 flourished to the north of it, in the following 

 manner. In the order Equisetales the 

 Calamites, which are dominant types in the 

 north are replaced hj Schizoneura and Phyl- 

 lotheca, the latter dominant and widespread 

 with several species, the former with but few 

 species and not becoming a dominant type 

 until the Mesozoic when it had spread beyond 

 the confines of Gondwanaland. In the order 

 Sphenophyllales one restricted species in India 

 and possibly in South Africa is the sole repre- 

 sentative of this common northern type and 

 evidently is an introduced form. The Fili- 

 eales are characterized by the genera Glos- 

 sopteris, Gangamopteris, Neuropteridium and 

 Palwovittaria, Gangamopteris appearing some- 

 what earlier and replacing the former in Vic- 

 toria and Brazil. 



Neuropteridium is very wide ranging but not 

 abundant, while Glossopteris is exceedingly 

 diversified, widespread, and very abundant 

 numerically. The genus Twniopteris, while 

 present, is not a characteristic or an abundant 

 type until the succeeding Mesozoic era, while 

 the various other fern genera which are present 

 are too indefinite or rare to be important ele- 

 ments in a discussion of the flora as a whole. 

 In the order Lycopodiales the southern forms 

 are similar to the northern (Lepidodendron, 

 Bothrodendron, LepidopMoios, Sigillaria) and 

 represent a southward migration to South 

 Africa and South America over land connec- 

 tions in those general regions. In the order 



Cordaitales the important northern type 

 Gordaites is replaced by the genus Nwggera- 

 thiopsis which is widely distributed through- 

 out Gondwanaland, reaching Tonquin and 

 China in the Mesozoic. The Cycadales are 

 few and of a doubtful nature. The Ginkgoales 

 are represented by the indefinite forms re- 

 ferred to Rhipidopsis and Psygmophyllum, 

 and are also harbingers of the Mesozoic fiora. 

 The Coniferales are also few in number and 

 somewhat indefinite in character and may be 

 neglected here. We thus see that of the six 

 dominant Paleozoic orders the Lycopodiales 

 and Sphenophyllales were represented in the 

 Glossopteris flora by only a few migrants. 

 The essentially post-Paleozoic Cycadales, 

 Ginkgoales and Coniferales are alike for both 

 the northern and southern floras, and the chief 

 contrasts are furnished by the fern-like plants 

 and the members of the Equisetales. Land con- 

 nections evidently became accessible toward 

 the close of the period for we find Glossopteris 

 and Phyllotheca in the Permian of northern 

 Eussia, while other survivors are found in the 

 Mesozoic of Germany, Sweden, China, etc. 



The precise age of the Glossopteris flora 

 has been a warmly disputed question for over 

 half a century, such eminent paleobotanists 

 as da Zigno, Sehimper and Feistmantel claim- 

 ing it to be Mesozoic (Jurassic), while Clarke, 

 the Oldhams and the Blanferds held that it 

 was of Paleozoic aga Arber's conclusion, one 

 largely accepted in recent years, is that the 

 Glossopteris-heaTcing rocks are homotaxial 

 with those of the Upper Carboniferous and 

 Permian of America and Eurojje. It was 

 found impossible to distinguish between the 

 Carboniferous and Permian periods so that 

 the epoch as a whole must continue to bear 

 the somewhat indefinite title of Permo- 

 Carboniferous. While it appears that isola- 

 tion alone could not have produced the re- 

 markable character of the Glossopteris flora, 

 Arber refrains from discussing climatic con- 

 ditions beyond the statement that the wide- 

 spread glaciation immediately antecedent to 

 the deposition of the earlier Glossopteris-heax- 

 ing sediments probably had a marked influ- 

 ence in this connection. It would have added 



