46 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



gium — then we must regard the leaf-cushion as a persistent 

 basal portion of the leaf remaining permanently attached to the 

 bark. The so-called "ligule-scar" 1 in Lepidodendron is really a 

 small pit from whose base the ligule springs. This structure 

 has been described by the late M. Hovelacque in his work on 

 Lepidodendron selaginoides. 2 



The leaf- cushions are arranged in steep spirals and are con- 

 tiguous, as in Lepidodendron ophiurus, Brongt., or more or less 

 distant, as in Lepidodendron rimosum, Sternb., or Lepidodendron 

 seyyentigerum, Konig, where the cushions end in tail-like pro- 

 longations, 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 conditions 

 of growth or age of the individual. This 

 is seen in Lepidodendron aculeatum, 

 Sternb. 



In some species, as in Lepidodendron 

 to. serpentigerum, Konig. the leaf -cushions 



Fig. 6. - Lepidodendron are alwa ? s disfcant as far as at P resent 

 Wortheni Lx. Leaf known, and the interfoliar space is orna- 

 cushion, natural size, mented with fine irregular wavy lines, 

 showing ornamentation and a somewhat similar form of orna- 

 ( - /cJ1 )- mentation of the bark appears to be a 



constant character on all species where the leaf-cushions are 

 distant. 



As a rule, the surface of the leaf-cushion is free from all orna- 

 mentation except the transverse notches, which are frequently 

 present on the lower portion of the keel. In some cases this may 

 be due to shrinkage of the tissues through decay, but probably it 

 is not always so caused. In Lepidodendron Wortheni, Lx., how- 



1 The "ligule" of MM. Bertrand and Hovelacque has been named the 

 " Adenoid Organ " by Prof. Williamson, who could not see in it the homo- 

 logue of the ligule of Selaginella and Isoetes. — See Williamson, Mem. XIX., 

 Phil. Trans., Vol. 184, pp. 9-10, 1893. 



2 Hovelacque, " Recherches sur le Lepidodendron selaginoides, Stern- 

 berg," Mem. de Soc. Linneenne de Normandie, Vol. XVII., fasc. I., 1S92. 

 Caen. 



