kidston: Vorkshire carboniferous flora. 9 



Hydatica prostrata Artis, pi. i. 



This plate shows a calamite stem with the roots attached. 

 It is now classed in the genus Pimiularia L. & H. In 

 Pinnulaiia are most probably placed the roots and rootlets 

 of many plants. Several authors refer to Pinnularia as the 

 roots and rootlets of Catamites and some Pinnutaria have 

 such an affinity — but likely not all. There is a considerable 

 difficulty in defining the species of Pinnutaria, and I have 

 usually been under the habit of including all the British 

 forms under Pinnularia capittacea L. & H., but some 

 botanists regard several species. The arrangement of the 

 rootlets appears to be almost the only character one has for 

 guidance, and this varies so much that great difficulties 

 arise in defining species. In the plate there is shown a 

 stem or rhizome of Catamites, and if this were sufficiently 

 well preserved for specific identification, the whole specimen 

 (including roots), would be named from it, but that not being 

 the case, the stem is passed over and the roots are named, 

 a very unsatisfactory mode of proceeding, but one which in 

 the present state of our knowledge of fossil plants, and the 

 desirability of having definite names for the fossils met with, 

 must be occasionally adopted. We may therefore call this 

 plant in the meantime Pinnutaria prostrata Artis sp., from 

 which the Pinnutaria capittacea L. & H., can scarcely be 

 separated. 



Elsecar, near VVentworth. 

 Catamites ramosus Artis. PI. ii. 



Leabrook .Quarry, near Wentworth. 

 Ficoidites furcatus Artis. PI. iii and iii bis. 



This is simply a specimen of Stigmaria ficoides but pro- 

 bably gives the first figure of the dichotomously divided 

 rootlets (PI. iii. bis, A. & B.). 

 Catamites approximatus Artis. PI. iv. 



This is not the plant generally regarded as the true 

 '■approximatus' but more probably a form of Catamites 



