532 MR ROBERT KIDSTON ON 



But irrespectively of the scientific aspect of this subject, from the practical side of the 

 question a grave difficulty arises, when the great majority of the specimens one has to 

 deal with only show fragments of the bark. How, under such circumstances, is it to be 

 determined whether the leaf-cushions were directed upwards or downwards, as this can 

 only be determined in any given species by the discovery of branching specimens or 

 examples on which the leaves are still attached to their cushions, for whatever the 

 position the leaf-cicatrice may hold in relation to its cushion, whether the cushion were 

 directed upward or downward, the leaf always rises upwards* In illustration of these 

 remarks, I may cite the case of Lepidophloios Dessorti, Zeiller,t the downward direction 

 of whose leaf-cushions is shown by the upward rising of a still attached leaf. As a 

 species of which it is impossible to determine whether the leaf-cushions were directed 

 upwards or downwards, Lepidophloios tumidus, Bunbury, sp.,|may be mentioned. In 

 such a case as Lepidophloios tumidus, how are we to decide as to whether the species is 

 a Lepidophloios or a Lomatophloios ? It certainly belongs to one of these two genera, 

 but to place it in either could only be guess-work, as it does not afford any data for 

 generic determination if we regard as of generic value the upward or downward direction 

 of the cushions ; and further, it will be shown presently that, in one species at least, the 

 leaf-cushions on the young branches are directed upwards, while those on the old stems 

 are directed downwards. I should not have entered so fully into this subject were it not 

 that some recent writers still treat Lepidophloios and Lomatophloios as distinct genera, 

 and have, further, included plants under one or other of these genera which the original 

 generic descriptions could in no case embrace. 



1849. Denny, H. " A Glance at the Fossil Flora of the Carboniferous Epoch, with especial 

 Reference to the Yorkshire Coal Field," p. 36, pi. i. (A paper read before the 

 Geol. and Poly tech. Soc. of the West Riding of Yorkshire, at Wakefield, March 

 8, 1849.) 



Mr Denny here figures an excellent specimen of Halonia, showing four dichotomies. 

 In his description of the fossil he says, p. 36 — " Of the genus Halonia, which, like 

 Lepidodendron, probably holds an intermediate place between the Lycopodiacece and the 

 Coniferce, four well-marked species occur, the gracilis, regularis, tortosa (? tortuosa), and 

 tuberculosa, at Low Moor and Dewsbury, — of the last species, one specimen in the 

 possession of the Philosophical Society, procured from the Sandstone at Potternewton, is 

 the most perfect example I have ever seen, and possesses peculiar interest, as not only 

 exhibiting the mode of branching of the genus, a point upon which nothing positive was 

 known, but also, apparently, combining the characters of the genera Halonia and Knorria ; 



* When the direction of the leaf-cushions has once been determined in any given species, of course in the case of 

 fragments which do not themselves give any evidence of the direction of the cushion, if they are of correqwnding age, 

 their direction may safely be inferred from the known direction, determined on more perfect specimens. 



t ZbttJiER, Flore foss. bassin houil. et perm, de Brive., p. 77, pi. xiii. fig. 1, and 1 B, 1892. 



X Lepidodendron (?) tumidum, Bunbury, Quart. Jour. Geol. Soc, vol. iii. p. 432, pi. xxiv. fig. 1. 



