ROOTS AND ROOTLETS. 39 



was merely the cast or impression of that exterior. They regarded the little pro- 

 jecting circles corresponding to those of my fig. 75, as identical with those of my 

 Plate XII, fig. 74, believing the former to be the portions of the bark upon which 

 the proximal ends of the rootlets were planted, whereas they are the actual 

 proximal ends of those rootlets. Specimens in my cabinet demonstrate that such 

 is the case, since in them the remaining distal part of each rootlet is seen passing 

 backwards through the stone to its opposite surface. 



A glance at the diagram of a longitudinal section of a rootlet with a portion of 

 the bark upon which it is placed (Plate XII, fig. 76) will probably make the history 

 of the specimen, fig. 75, intelligible. A fragment of such a bark has been 

 reduced to the condition seen in Plate XII, fig. 74. That this occurrence took 

 place is shown by the fact that casts, which I have made of the surface of that 

 specimen, correspond almost exactly with what we see in Plate XIV, fig. 75. The 

 outer surface of the supposed bark was undisturbed, as at fig. 76, d". Each long 

 rootlet, 76, g, had either decayed from its tip backward or had been abruptly broken 

 off near the surface of the bark, where a little of the outer cylindrical wall of each 

 rootlet stood in relief, as at fig. 76, g" g", forming a funnel-shaped cup, as in Plate 

 XII, fig. 74, g. At the bottom of this cup there would project the cone of the 

 rootlet cushion, as in the section Plate X, fig. 44, ti ; embedded in mud, the 

 future matrix of the specimen fig. 75, that mud would fill the cavity, fig. 76, g , 

 and also surround its external wall and invest the outer surface of the bark, d". 

 The unshaded paper to the right of the bark surface, d" d", thus represents the 

 outlines of a section which would be identical with a similar section made through 

 one of the rootlet bases of Plate XIV, fig. 75. 



Plate XII, fig. 40, is a Stigmaria, the interpretation of which was not easy 

 on a merely casual glance. The fragment is but a portion of a much larger 

 specimen, almost identical with, and from the same locality as, that from the 

 interior of which fig. 39 was extracted. "We see from fig. 38, which represents 

 the upper end of fig. 39, that all the vascular tissues of that cylinder are well 

 preserved ; but both vascular and cellular tissues have disappeared from the area, 

 // of fig. 40, with the exception of a confused mass of vascular bundles ; these are 

 evidently the remains of such portions of rootlet bundles as passed through the 

 bark, like those seen on the exterior of fig. 39, but which were left exposed on the 

 decay of the cortical tissues. At fig. 40, g g, the rootlets of one side of the 

 specimen pass outwards to the right hand, each in a flattened condition. The 

 surface d is a cast of the outside of the bark opposite to that which supplied the 

 rootlets, g g. The rootlets of d have not collapsed and become flattened after 

 they were invested by the then plastic matrix, though they subsequently disap- 

 peared, leaving empty cylindrical cavities which pass downwards and outwards 

 through the stone. In several of these cavities the vascular bundle of each 

 rootlet can still be detected, and two or three of the rootlet cavities present similar 



