74 Reign of the Gymnosperms. 



" This reign of the Gymnospermous dicotyledons is divided 

 into two periods ; the first, in which the Coniferse predomi- 

 nate, and in which the Cycadese scarcely appear ; the second, 

 in which this family becomes predominating in the number 

 of species, in frequency and variety of generic forms. The 

 latter may be divided into many epochs, each presenting pe- 

 culiar characters. 



" III. Vosgian Period. — This period, which does not ap- 

 pear to have been of long duration, and comprehends only 

 the variegated sandstone properly so called, presents the fol- 

 lowing characters ; Ist^ The existence of ferns, pretty nume- 

 rous, of forms very often anomalous, evidently constitut- 

 ing genera now extinct, and which are not found even in the 

 most recent formations ; such are the Anomopteris and the 

 Crematopteris. Stems of arborescent ferns are more fre- 

 quent than during the Jurassic period ; true Equisetums are 

 very rare ; the Calamites, or rather perhaps the Calamoden- 

 drons, are abundant. 2d, The Gymnosperms are represented 

 by two genera of Coniferse, Voltzia and Haidingeria, of which 

 the species and specimens are very numerous. The Cycadeae, 

 on the contrary, are very rare. M. Schimper mentions only 

 two species founded on two unique specimens of a very imper- 

 fect character, and the determination of which may be consi- 

 dered doubtful. 



" This consideration appears to me to separate completely, 

 in a botanical point of view, the period of the variegated 

 sandstone from that of the Keuper, although both are placed 

 by geologists in the trias-formation. For the Cycadese become 

 very abundant in the Keuper, are perfectly characterised, 

 and often analogous to those of the Jurassic period ; while 

 the Coniferae of the variegated sandstone are, on the con- 

 trary, wanting in this formation. 



" IV. Jurassic Period, — This period is one of the most ex- 

 tensive by the formations which it comprehends, and the 

 variety of different special epochs of vegetation which it em- 

 braces ; although we cannot refuse to comprehend, under a 

 common title, epochs during which very analogous forms have 

 succeeded each otner. It thus comprehends from the Keuper 

 inclusively, up to the Wealdean formations. In fact, we find 



