XIV] FOSSIL LYCOPODIALES 73 



identical with Pleuromeia Sternbergi. An examination of a 

 cast of the type-specimen in the Berlin Bergakademie led me 

 to regard the fossil with some hesitation as a true Sigillaria, 

 but a more extended knowledge of Pleuromeia lends support to 

 the view adopted by Potoni^^ that Blanckenhom's plant is not 

 generically distinct from Pleuromeia Sternbergi. The resem- 

 blance between Sigillaria oculina and some of the Palaeozoic 

 species of Sigillaria emphasised by Weiss ^ has given rise to the 

 belief that the genus Sigillaria persisted into the Triassic era ; it 

 is, however, highly probable that the Bunter specimen has no 

 claim to the generic name underwhich it has hitherto been known. 



The Bunter Sandstone in which Pleuromeia is the sole 

 representative of plant-life, at least in certain localities, is 

 usually considered to be a desert formation. We may not be far 

 wrong in accepting Fitting's suggestion that in this isolated 

 species we have a relic of the sparse vegetation which was able 

 to exist where the presence of lakes added a touch of life to the 

 deadness of the Triassic desert. 



Pleuromeia is recorded by Fliche as a rare fossil in the 

 Middle Trias of France in the neighbourhood of Luneville*- 



Herbaceous fossil species of Lycopodiales. 



The history of our knowledge of fossil representatives of the 

 Lycopodiales, as also of the Equisetales, affords a striking 

 illustration of the danger of attempting to found a classification 

 on such differences as are expressed by the terms herbaceous 

 and arborescent in the sense in which they are usually 

 employed. As we have seen*, the presence of secondary wood in 

 stems of the Palaeozoic plant now known as Calamites led so 

 competent a botanist as Adolphe Brongniart to recognise a 

 distinct generic type Calamodendron, which he placed in the 

 Gymnosperms, reserving the designation Calamities for species 

 in which no indication of secondary thickening had been found. 



Similarly, the genus Sigillaria was regarded as a Gymno- 

 sperm because it was believed to be distinguished from 



1 Potonid (04) Lief ii. ^ Weiss, C. E. (86). 



s Fliche (03). * Vol. i, p. 300. 



