﻿4 WEISS AND Lomax, Lepidodendron selaginoides. 



base, and thus the scar resembles to a certain extent those 

 of Bothrodendron. It is interesting to find on comparing 

 our specimen with that figured by Binney, that the origin 

 of a branch in the same plant may be represented in the 

 one case by a prominence, in the other by a depression. 

 The same differences are found in ulodendroid and halo- 

 nial branches of other lepidodendroid plants. In our 

 specimen there appear to have been two rows of branches, 

 on opposite sides of the stem, an arrangement which 

 seems to have been common in the Lepidodendraceae. 



It is a point of particular interest that while sections 

 of the main axis show it to have possessed a considerable 

 amount of secondary wood evenly distributed around the 

 central axis, the lateral branches have the structure of 

 small branches of Lepidodendron selaginoides, without 

 secondary growth (see Jig. I of the Plate). Thus, as first 

 suggested by Binney, the Sigillaria vascularis was only an 

 older stage of Lepidodendron vasculare. In the latter form 

 the secondary wood, when developed, often presents a 

 crescent-shaped appearance, or, if continuous all round, the 

 primary wood is developed more strongly on one side than 

 the other. This is not usually seen in the stems originally 

 named Sigillaria vascularis, and it would seem quite 

 probable that these represent the upright main stem, 

 while the lateral branches showed an eccentric develop- 

 ment of secondary wood, such as is met with in the lateral 

 branches of some of our phanerogamic trees of to-day. 

 If the main stem gave off, as it seems, lateral branches of 

 slighter girth, while the branches themselves divided 

 dichotomously, the habit of Lepidodendron selaginoides 

 must have resembled very nearly the reconstruction of 

 Lepidodendron elegans, figured by Dr. Scott (:oo).* 



As will be seen from the longitudinal section repre- 



* " Studies in Fossil Botany," fig. 47, p. 117. 



