ROOTS. 5 



Bally, well skilled in the art of making moulds, was employed to obtain exact casts 

 of the two most important of the above trees. These casts, which are now pre- 

 served in the Geological Museum of Owens College, are represented in Figs. 1 and 

 2. That represented by Fig. 1 is 2 feet 6 inches high. The circumference of its 

 upper extremity is 7 feet 9 inches, and 8 feet 5 inches at two feet from the floor. 

 From * to * measures 10 feet. Though the full length of the spreading roots which 

 originally existed is not exhibited in either of these casts, both well show some of 

 their primary dichotomous ramifications. The specimen, Fig. 2, is 6| feet high ; its 

 circumference at its upper extremity is 7 feet 10 inches, and 10 feet 6 inches at two 

 feet above the floor. The longitudinal ridges and furrows seen on these casts do 

 not represent the vertical flutings of a Sigillaria, neither do we find on the roots 

 any traces of the rootlet-scars so conspicuous in Figs. 5 and 6. We learn from 

 the specimen, Fig. 2, that in all probability no portion of the true aerial stem is 

 preserved in Fig. 1. It is a mere mass of coalesced roots. The upper part of 

 Fig. 2 is doubtless cauline. The disappearance of all traces of leaf-scars from the 

 latter, and of rootlet-scars from both, is due to the same cause, viz. the internal 

 exogenous growth, which increased the diameter alike of the vascular and cortical 

 zones of both stem and root. This expansion necessarily caused the outer bark 

 to become fissured and its superficial portions to be thrown off; and, since the 

 cicatrices left by both leaves and rootlets were confined to the superficial cortex, 

 when this was cast off they inevitably disappeared along with it. This gradual 

 disappearance of both can readily be traced in numerous specimens. 



As is now well known, the primary roots given off by all these trees are four in 

 number. Fig. 1 only exhibits two (a, a) of them. Three such (a, a, a) are seen 

 in Fig. 2. In Fig. 1 both the primary roots, a, a, dichotomise. In Fig. 2 only one 

 such dichotomy is seen at a, but as the tree originally stood at Dixon Fold more 

 such were visible. 



The thickness of each primary root (a) is often enormous in the older trees. 

 The tetramorphic arrangement is best seen when the specimens are inverted so as 

 to show their inferior surfaces. Plate II, fig. 3, represents one such base now in 

 the Museum of the Leeds Literary and Philosophical Society. 1 Such specimens 

 are frequently marked by the defined crucial suture seen in Figs. 4 and 6, a fact 

 which was first pointed out by Mr. Binney in 1854. 2 These sutures indicate the 

 surfaces of contact of the four several roots. In Fig. 3 they are very feebly pre- 

 served. The circumference of the root a at e-h is 3 feet ; of b at e-g is 3 feet 2 

 inches ; the breadth from g to h is 21 inches, and from e to/ 18 inches, whilst from 

 a to d is 37^ inches. 



1 This figure is lithographed from a photograph, for which I am indebted to Professor Miall, the 

 accomplished Curator of the Museum. Figs. 1 and 2 are also lithographed from photographs taken for 

 me by A. Brothers, Esq., F.R.A.S., of Manchester. 



2 ' Quarterly Journal of the Geological Society,' vi, p. 21, figs. 5 and 7. 



