1 1 AGE OF FLORAS 5 



The horizon of the plant-bearing beds in the Old Red of 

 Scotland can in most cases be determined by the associated 

 fish faunas. Important specimens, including Psilophyton in a 

 petrified condition 1 , recently discovered in the Dryden Shales at 

 Rhynie, Aberdeenshire, by Dr Mackie 2 are, however, exceptional 

 in that the precise horizon has not yet been ascertained. These 

 beds are, however, regarded as not younger than Middle Old 

 Red 3 , but since this genus is known to range throughout 

 Devonian time, the precise horizon of these beds is immaterial 

 from this point of view. 



Ireland. The plant-bearing sandstones of the Old Red of the 

 South of Ireland are referred to the Upper Old Red (Upper 

 Devonian) on the evidence of the associated fish remains. 



England. The few plants known from the Devonian of England 

 come from the type beds of the Upper Devonian (Baggy or 

 Cucullaea beds) in North Devon. 



Belgium. Two plant-bearing horizons occur in Belgium which 

 on stratigraphical grounds are assigned to the Lower arid Upper 

 Devonian respectively. These are the "Poudingue de Burnot" 

 and the "Psammites du Condroz." 



Germany. A small but important flora from near Herborn 

 in Hesse-Nassau has been recently referred to the Silurian. On 

 the fossil plant evidence, however, there can be no doubt that 

 it is of Devonian age, and belongs, in all probability, to the 

 Upper Devonian. 



Bohemia. The large flora from the horizon (hi) of Barrande's 

 system of classification of the Devonian rocks of Bohemia was 

 likewise originally referred to the Silurian. The Devonian age of 

 these beds is now, however, admitted. More recently it has been 

 found 4 that Stringocephalus Burtini, a characteristic Middle 

 Devonian fossil, occurs on a yet higher horizon (h3) and thus 

 the plant-bearing beds clearly also belong to this same zone. 



Norzvdy. The evidence as to the horizon of the plant-bearing 

 beds in Eastern and Western Norway is purely palaeobotanical. 

 There is no zoological evidence. Nathorst, as we think rightly, 



1 For the case in support of this identification, see pp. 24-26. 



2 Mackie (1914); Home and Mackie (1917). 



3 Kidston and Lang (1917), p. 762, footnote. * Jahn (1903). 



