LEPIDODENDRON AND SIGILLARIA. 



81 



inch across. There is no doubt that we have here the stem of a Lepidodendron cut 

 across where the woody cylinder has commenced to divide, but lower down than where 

 the whole stem dichotomizes into two, as is so generally seen in Lycopodiacece. 



Figs. 2 and 3 (magnified three and a half diameters) represent the two vascular 

 axes. Their outer portions show structure, in the large scalariform tubes generally found 

 constituting the woody cylinder of Lepidodendron. There is no trace of anything 

 resembling medullary rays. The whole of the medulla has been replaced by white 

 carbonate of hme. Fig. 2 represents the lower and fig. 3 the upper of the bodies seen 

 in fig. 1. 



§ 3. The Specimen {Sitjillaria vascularis) No. 33. Plate XIV, figs. 4, 5, 6. 



Specimen No. 33 (Plate XIV, fig. 4, magnified three and a half diameters) is a trans- 

 verse section of Sigillaria vascularis, found by me in the " Bullion" seam of coal (marked 

 ** in the section of the Lancashire Coal-measures, p. 12) at SpaClough near Burnley. 

 It is of an elongate-oval form, and measures one and six eighths of an inch across its major, 

 and seven eighths of an inch across its minor axis. The specimen is enclosed in its matrix 

 of carbonate of lime. The two apple-shaped vascular axes, parted by some fine 

 orthosenchymatous tissue, and surrounded by a radiating cylinder of vascular tissue of a 

 wedge-shape, containing medullary rays, appear to have been enclosed in a zone of delicate 

 parenchyma, which, having partially disappeared, has been more or less replaced by 

 carbonate of lime. This is succeeded by a zone of strong parenchyma, which gradually 

 passes into long utricles or tubes, arranged in radiating series ; and throughout all pass 

 the vascular bundles, leading from near the central cylinder to the leaves. The external 

 covering appears to have consisted of an outer bark, now converted into coal. 



Pigs. 5 and 6 (magnified ten diameters) represent the right and left apple-shaped 

 bodies free from the stem. Their axes are seen to be composed of large scalariform 

 utricles or tubes, and of fine orthosenchymatous tissue near the notches in the outer lines. 

 They are surrounded by a cylinder of radiating vascular tissue, and a portion of the zone 

 of fine parenchyma envelopes it. 



A similar example of dichotomization of the stem of Halonia regularis, hereinafter 

 described, also shows the division of the vascular axis of the stem into two, like those of 

 Lepidodendron and Sigillaria. 



Brongniart, in speaking of the stems of Lycopodiacece} says, " Parmi ces dernieres 

 [Lycopodiacees] ce mode de ramification tient a leur developpement entierement terminal, 



1 ' Histoire des Vegetaux fossiles,' Tome ii, p. 4. 



