210 Bernard Smith — A Lepidodendroid Stem, 



The leaf-cushions are thus entirely separate from one another. 

 Two examples of Lepidodendron serpentigerum,^ Konig, derived from 

 Newcastle and now preserved in the British Museum, have been 

 found to measure I'l cm. and 1-6 cm. respectively from scar to scar; 

 but the cushions occupy a much greater relative proportion of the 

 external surface of the stem than they do in the present case, whilst 

 they are connected with one another by tail-like prolongations 

 running from the lower extremity of the leaf-cushion above to 

 the upper extremity of that beneath. It appears that it is not 

 uncommon in some species of Lepidodendra to find the cushions 

 separated by a certain amount of bark, as in the instance above 

 cited, where the two occupy almost equal areas. But it certainly 

 is unusual that such a relatively large proportion of the whole area 

 of the stem or branch — roughly three-fourths of it — should consist 

 of bark. To quote Mr. Kidston ^ : *' The leaf-cushions are arranged 

 in steep spirals and are contiguous, as in Lepidodendron opliiurus, 

 Brongt., or more or less distant, as in Lepidodendron rimosiim, Sternb., 

 or Lepidodendron serpentigertim, Konig, where the cushions end 

 in tail-like prolongations, by which the various members of the 

 same spiral series are connected to each other. In some species, 

 however, the leaf-scars are contiguous or more or less distant, 

 according to the growth or age of the individual. This is seen in 

 Lepidodendron acideatum, Sternb. In some species, as in Lepidodendron 

 serpentigernm, Konig, the leaf-cushions are always distant, so far as 

 at present known, and the interfoliar space is ornamented with fine 

 irregular wavy lines, and a somewhat similar form of ornamentation 

 of the bark appears to be a constant character in all species where 

 the leaf-cushions are distant." 



The bark is wrinkled longitudinally, the fine corrugations 

 anastomosing at small angles. The striae do not sweep round the 

 cushions, as in L. serpentigernm, L. veltheimianum, L. corriigatum, 

 and some other species ; but terminate sharply against them. At 

 the widest part of the cushion they sweep over its angles, maintaining, 

 however, their longitudinal direction. We might compare these 

 striae with those of L. distans,^ Lesqr,, which also end abruptly at 

 the cushions, but do not encroach upon them. 



The general appearance, the shape of the specimen, and the fact 

 that it has, in all probability, not been considerably crushed, all 

 seem to favour the idea that it is a part of an old branch or stem. 

 Moreover, in some Lepidodendra we find that as the stem advances 

 towards maturity, the leaf-cushions often tend to become more 

 elongated, especially in cases where the cushions of the young 

 branches are as broad, or broader than long. For example, those 

 of L. dichotomum, Zeiller, are shorter than broad ; those of Z. obovatum, 

 Sternb., as long as broad. So we might argue that the length of 



1 Registered number 38,089. 



" Kidston, " Carboniferous Lycopods and Sphenopbylls " : Trans. Nat. Hist. Soc. 

 Glasgow, N.S., vol. vi, p. 46 (1899-1900), 1901. 



^ Eegarded as identical with L. serpentigernm, Kon., by Kidston : Cat. Palfcoz. 

 Plants Brit. Mus., p. 157, 1886. 



