64 



THE ARCIIAEOPTERIS FLORA 



[CH. 



moment it may be retained as a distinct tyj^e in a position close 

 to Sphenopteridium. 



Sphenopteris, Brongniart, 1822. This well-known but well- 

 nigh indefinable type of compound frond with rounded pinnules, 

 more or less deeply lobed and contracted at the base, appears to 

 be rarer in Devonian rocks than Sphenopteridium. It, however, 

 occurs in England, Ireland, Belgium and several other regions 

 in Upjjer Devonian rocks. 



Distribidion. From Upper Devonian onwards. 



Lycopsida. 



Bnthrodendron, L. et H., 1885 

 (Fig. 37). This well-known genus is 

 of frequent occurrence in Devonian 

 rocks. There has been some ten- 

 dency to include the Devonian species 

 in a distinct genus Cyclostigma^, as 

 originally suggested by Haughton in 

 1859. This, however; can now hardly 

 be justified^. There is little doubt 

 that the best known of the Devo- 

 nian species, B. Kiltorkense, occurring 

 in Ireland and Bear Island, is a 

 thoroughly typical representative of 

 the genus, as the recent studies 

 of Nathorst and Johnson clearly 

 show. 



Practically all the organs of B. 

 Kiltorkense are now known. The 

 lower part of the trunk consists of a 

 Stigmarian rhizophore, the features 

 of which agree closely with the 

 Stigmarias of the Coal Measures. 



Fig. 37. Bothrodendron Kil- 

 torkense, (Haugh.), from the 

 Upper Old Red of South Ire- 

 land. Stem with leaf scars. 

 (Reduced |- nat. size.) Speci- 

 men No. 20 Devonian Plant 

 Coll., Sedgwick Museum, 

 Cambridge. (W.Tams photo.) 



According to Johnson^, " the 

 leaves are cleai-ly arranged in whorls at first, but become 

 distant and quincuncially arranged in older stems, owing to 



1 This term is in any case several times preoccupied by recent Angiosperms . 



2 Johnson (1913), especially p. 505. " Ibid. (1913), pp. 523-4. 



