LEPIDODENDREAE. 2 1 1 



two, and the genus is further distinguished by the quite peculiar configura- 

 tion of the leaf-cushions. These are not flat as in Lepidodendron, but are 

 developed in the form of tall steep-sided cones which are crowded close 

 together and gird the stem with an armour of leaf-bases, just as in our 

 modern Cycadeae. In addition to this the base of the cushion is trans- 

 versely rhombic in form, the angles at the lateral edges being acute and 

 those at the median very obtuse, and thus the cushions differ altogether in 

 habit from the elongated cushions of Lepidodendron, and have the appear- 

 ance of scale-like leaves. From their crowded position they necessarily 

 cover one another like the tiles in a roof; in looking at them from the out- 

 side we get sight of the anterior portion only of one pair of facets of each 

 cushion, and the areola of separation of the leaf-blade lies on the most 

 anterior point of its margin. This areola has a similar outline to that of 

 the whole cushion, its lateral edges are very sharp, and as compared with 

 that of Lepidodendron it is strongly compressed in the median direction. 

 Upon it are found the usual three trace-points, the middle one of which 

 corresponds, as we saw, to the transverse fracture of the vascular bundle. 

 We said just now, that in the outside view we can see only one of the two 

 pairs of facets, and now comes the somewhat difficult question whether this 

 is the upper or the lower one. On this depends the determination of the 

 upper and lower side of the fragments of stem. If it is the lower pair, then 

 the scales of the armour were directed obliquely upwards and bore the scar 

 above on the apex, in the opposite case they were reversed and the scar is 

 placed on the lowest point of their margin. In the former case the de- 

 velopment of the lower pair is the greater, in the second that of the upper, 

 a point which Stur has discussed at length. Now the views of authors are 

 much divided on this question, the scar being placed below in Sternberg 

 and Schimper 1 , above in Corda 2 , O. Feistmantel 3 and Geinitz 4 and 

 recently in Renault 5 , while Goldenberg disposes his pieces in more than 

 one way and divides them accordingly into the genera Lepidophloios and 

 Lomatophloios, giving to the latter the species which he thinks had erect 

 scales and to the former those with the scales reversed. Weiss c however has 

 reunited the two groups ; he insists very justly on the subjective character 

 of Goldenberg's division, in wTiich everything depends on the disposition of 

 the specimens. He seeks also to lessen the value of the other marks which 

 Goldenberg adduces in support of his genera. Among these may be men- 

 tioned the form of the three trace-dots on the scar, which obviously depend 

 too much on the preservation to be capable of being used in this manner ; 

 and next the medullary cylinders of the Artisia kind on which Goldenberg 

 relies, which are said to be smooth in Lepidophloios, transversely furrowed 



1 Schimper (1). 2 Corda (1). 3 O. Feistmantel (3). 4 Geinitz (8). 5 Renault (2). 

 6 Weiss (1). 



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