478 Palaeontologie. 



Ginkgoales in other parts of the world — In Australia, 

 South Africa, South America, China, Japan, North 

 America, Greenland, Franz Josefs Land, Siberia, 

 and throughout Europe — demonstrates the former vigour of 

 this class of plants of which but one member survives. 



d. Ferns. Although many of the Mesozoic ferns are pre- 

 served only in the form of sterile fronds and are of little 

 botanical interest, several examples of fertiie leaves are known 

 which it is possible to compare with modern types. The 

 Polypodiaceae, representing the dominant family of recent ferns, 

 are met with in nearly all parts of the world and possess the 

 attributes of a group of plants at the zenith of its prosperity. 

 We may confidently state that so far as the somewhat meagre 

 evidence allows us to form an opinion, this family occupied a 

 subordinate position in the composition of Mesozoic floras. 

 Polypodiaceous sporangia have been met with in Palaeozoic 

 rocks, and their existence during the Mesozoic period is not 

 merely a justifiable assumption, but is demonstrated by the 

 occurrence of undoubted species of Polypodiaceae. It seems 

 clear, however, that this family did not attain to a position of 

 importance until the Mesozoic Vegetation gave place to that 

 w^hich characterises the present period. The Osmiindaceae, 

 now represented by five species of Todea and four of Osmunda, 

 flourished over the greater part of Europe during the Rhaetic 

 and Jurassic periods ; their remains habe been recorded from 

 England, Germany, Scandinavia, Russia, Poland, 

 Siberia, and Greenland, also from North America, 

 Persia, and China. 



Similarly the Schizaeaceae, were among the more abundant 

 ferns in the jurassic Vegetation. The Cyatheaceae, a family 

 that is now for the most part confined to the tropics, con- 

 stituted another vigorous and widely spread section in the 

 Jurassic period; we find them in Jurassic rocks of Victoria, 

 as well as in severa! regions in Europe, North America, 

 and the Arctic regions. 



The fertiie fronds of many of the fossil Cyatheaceae bear 

 a striking resemblance to that isolated survivor of the family 

 in Juan Fernandez — Thyrsopteris elegans. It is true that 

 a considerable number of ferns of Jurassic and VVealden age 

 have been discribed by the generic name Thyrsopteris without 

 any adequate reason ; but, neglecting all doubtful forms, there 

 remain several types represented in the Jurassic flora of 

 Siberia, England, and other parts of the world, which 

 enable us to refer them with confidence to the Cyatheaceae and 

 to compare them more particularly w-ith the sole existing species 

 of Thyrsopteris. The Gleicheniaceae, at present characteristic 

 of tropical and southern countries, were undoubtedly abundant 

 in the northern hemisphere in early Cretaceous days; abundant 

 traces of this family are recorded from Greenland as well as 

 from more southern European latitudes. 



