CARBONIFEROUS LYCOPODS AND SPHENOPHYLLS. 



45 



Extending both above and below the leaf-scar is a central keel, 

 which often bears transverse notches on its lower part. Above 

 the leaf-scar and in the line of the central keel is a small 

 cicatricule (c), which has been named by Stur the ligide scar. 

 This little cicatricule is immediately above the leaf-scar in 

 Lepidodendron aculeatum, Sternb., fig. 4c. In Lepidodendron 

 rimosum, Sternb., it is placed a short 

 distance above the leaf-scar (fig. 5). 

 Above the ligule-scar is a transverse 

 triangular notch (fig. 4e), which has been 

 regarded as the homologue of the 

 "sporangium attachment" by Stur.^ 



The area surrounding the leaf-scar is 

 called the field (d). In most species of 

 Lepidodendron immediately underneath 

 the leaf -scar are two oval pits (/), one 

 on each side of the keel. These also 



appear to be glandular or secreting Fig. 5. - Lepidodendron 

 organs." Some Lepidodendra, such as 

 Lepidodendron dichotornum, Zeiller (not 

 Sternb. ?), do not possess them. ^ 



On many specimens the so-called ligule-scar cannot be observed, 

 but as it is very small, only well-preserved examples can be 

 expected to show it. In a less degree the same remark applies 

 to the " sporangium notch." I am inclined to think, however, 

 that sometimes these are absent from some individuals— an 

 absence which cannot be ascribed to an imperfect preservation of 

 the fossil. Specimens in my collection support this view. 



If we regard the so-called " ligule scar " of Lepidodendron as 

 homologous with the ligule-scar occurring in Selaginella—axid 

 this interpretation finds support in the investigations of Mr. 

 Maslen,* who describes the occurrence of a ligule on the 

 sporophyll of Lepidostrobus immediately in front of the sporan- 



rimoaimi, Sternb. Leaf 

 cushion, natural size 

 (No. 2438). 



1 Stur, Culm Flora, p. 228, and Explan. to PI. XIX., fig. 1. 



= Transpiration openings of Potonie, Lehrb. d. PJlanzenpala>ontologie, 

 p. 220. 1899. 



3 Zeiller, Flore fo-^%. Bassin HouU. d. Valenciennes, PL LXVII., fig. 1. 



* Annals of Botany, Vol. XII., No. XLVL, 1898, p. 257. This'.is referred 

 to more fully under Lepidostrobus. 



