30 TRANSACTIONS, NATURAL HISTORY SOCIETY OF GLASGOW. 



some of the Carboniferous Lycopods, that at present a provisional 

 classification only is possible. With the exception of Lepidoden- 

 dron, the fructification of all the other genera is imperfectly 

 known. Hence it is only possible to define the genera of the 

 Carboniferous Lycopods and their relationship to each other in a 

 tentative manner. 



It is necessary, therefore, in the absence of fuller information 

 regarding their fructification, to depend largely for the classifica- 

 tion of the Carboniferous Lycopods on characters derived from 

 impressions of the outer surface of the plants, which, in addi- 

 tion to showing the structure of the leaf -scar, also show in many 

 cases the position held by the fructification on the stem. The 

 structure of the fructification is, of course, the most important 

 and only satisfactory basis on which to found a reliable classifica- 

 tion, and when this is known it is used, but, as already stated, 

 there are few cases where it is available. 



The following classification may, therefore, be adopted pro- 

 visionally : — 



LYCOPODIALES. 



A. LYCOPODITEiE. 



Plants of moderate size, whose stems probably attained a 

 diameter of several inches. In growth and habit resembling 

 Selaginella and Lycopodium. Leaf-scars imperfectly defined and 

 not possessing the prominent leaf-cushions of Lepidodendron. 

 Vascular cicatricule of leaf single, unaccompanied by the lateral 

 parichnos. Fructification in the form of terminal cones or 

 sporangia placed in the axils of the leaves Leaves small. 



I. Lycoptodites, Goldenberg, 1855 (Brongt. emended). 

 II. Archceosigillaria, Kidston, n.g. 



B. LepidodendrejE. 



Plants attaining to arborescent dimensions and ramifying by 

 repeated dichotomy. Stems bearing fusiform or rhomboidal 

 cushions, distant or approximate, arranged quincuncially, more 

 or less prominent, and to some part of which are attached the 

 single-nerved linear lanceolate or grass-like leaves. After the 

 fall of the leaf, the cushion bears a well-defined leaf-scar, varying 

 in shape, but generally more or less transversely rhomboidal, 

 with upper and lower angles rounded and lateral angles acute. 



