CONCLUSION. 



307 



xegarded as giving more than an approximate estimate of tie 

 •composition of eacli flora. It is probable that the vegetation 

 which has left fairly abundant traces in the Wealden sediments 

 of the South-East of England and in the Inferior Oolite beds of 

 Yorkshire, flourished under very similar climatal and physical 

 ■conditions. 



A comparison of the Inferior Oolite plants with those of Ehsetic 

 age from Germany, Scania, and other regions leads ns to recognize 

 a few examples of what appear to be identical species, e.g., Podo- 

 zamites lanoeolatus and Sphenopteris princeps. Several instances of 

 closely related types have also been pointed out in the introductory 

 and systematic sections of this volume. 



We may next briefly consider some of the more conspicuous 

 ■members of the Inferior Oolite flora from the point of view of 

 "their resemblance to other fossil types as well as to recent plants. 



EansBiALES. — Eq^uisetites eolumnaris is one of the commonest and 

 most characteristic plants in the Yorkshire flora. Its abundance 

 'lends support to the view that the small seams of coal met with 

 in the strata of the Estuarine Series were probably in great measure, 

 if not entirely, formed from the remains of the Equisetaceous 

 plants which grew in the Jurassic swamps. The thicker stems 

 described under the name Equisetites Beani are comparable in size 

 to E. arenaceus of Triassic age, and surpass in diameter the 

 characteristic Ehsetic form E. Muensteri. Compared with such 

 "Wealden species as Equisetites Lyelli and E. Burchwrdti the Inferior 

 Oolite Equisetacese are distinguished by the greater thickness of 

 their stems, and in this respect they carry us a stage further from 

 the modern Horsetails towards the arborescent representatives of 

 the Equisetales, which flourished during the Triassic and Palseozoic 

 ■epochs. 



FiLicES. — Among the Inferior Oolite ferns there are several 

 species which cannot be referred to any particular subdivision of 

 the fllices, but on the other hand we have sufficient evidence in 

 many cases to admit of a satisfactory identification of family 

 -affinities. The species Sagenopteris Phillipsi, which for reasons 

 already stated I have included among the Alices rather than the 

 Ehizocarpese, may not improbably belong to the Polypodiaceae, 

 but of this we have not sufficient evidence. The species is of 

 interest as a common type, which forms a connecting link on 

 i;he one hand with the older and larger Eheetic forms Sagenopteris 



