FILICES. 159 



very peculiar form, and in these points they agree exactly with the axes of 

 recent fern-leaves. There are also in very many cases longitudinal sub- 

 epidermal regularly disposed bands of sclerenchyma, which extend more or 

 less far into the parenchyma. Corda l , to whom we are indebted for the 

 first examination into the anatomical details of these remains, has divided 

 them into numerous genera founded essentially on the form and position of 

 the concentric bundles of the wood. Later authors, with a more superficial 

 treatment of the subject, have on the whole adopted Corda's terminology, 

 though Brongniart 2 carefully insisted that this distribution was quite pro- 

 visional, since an axis of a lower order of branching often differs in structure 

 from the main axis in the same species, and that the two would therefore in 

 Corda's system be placed in different genera. This restriction has ultimately 

 been applied in practice by Williamson 3 , who has included by far the larger 

 number of these bits of leaf-stalk in the genus Rhachiopteris, rightly keeping 

 a few only separate from the rest, because they are distinguished by special 

 peculiarities of structure in thick and thin pieces alike. The leaf-stalks 

 occur in very many cases as isolated detached fragments, especially in the 

 often-mentioned calcareous nodules of the Coal-measures and in the 

 siliceous pebbles of Grand' Croix ; but they have sometimes been found in 

 thick bundles interwoven with numerous roots, a state of preservation to 

 which Corda has given the generic name of Tempskya, but which is some- 

 times also termed Endogenites, Spreng., though this appellation belongs 

 particularly to the wood of palms. It is obvious then that this genus can- 

 not be maintained as it is, but it may be conveniently employed as a general 

 term for this particular state of preservation, so that Zygopteris for example 

 would be known both in the free state and in the Tempskya-condition. 

 We may observe here briefly that the adventitious roots of Temskyae 

 which are interwoven with the leaf-stalks show thoroughly the normal fern- 

 structure with a central radial usually pentarc or hexarc vascular bundle. 



We now proceed to notice the most important of Corda's 4 genera, all of 

 which come from the Coal-measures of Bohemia. The transverse sections 

 of Selenopteris 5 , Anachoropteris 6 , and Gyropteris 7 show a single bundle, 

 which in the last genus is coiled, in the first is crescent-shaped, and in 

 Anachoropteris is in the shape of a horse-shoe with involute extremities. 

 Next comes Selenochlaena resembling Selenopteris and founded on Cotta's 8 

 Tubicaulis dubius and Solenites, and Zygopteris founded on his Tubicaulis 

 primarius. In the latter form, of which through Renault's 9 researches we 

 know the stems and fructification, the bundle has somewhat the shape of a 

 Latin H. Finally, in Kalopteris 10 besides the crescent-shaped bundle of 



1 Corda (1). 2 Brongniart (2), p. 85. 3 Williamson (1), VI. * Corda (1). 5 Corda 

 (1), tt. 53, 54- 6 Corda (1), tt. 56, 57. 7 Corda (1), t. 54. Cotta (1). Renault (5). 

 10 Corda (1), t. 19. 



