78 PIlOCEEDrN"GS OF THE GEOLOGICAL SOCIETT. [Apr. 28, 



is rather more than an inch in diameter and quite uncompressed ; 

 and, owing to the axis of the stem having slipped out of the speci- 

 men, the perforations in the narrow ends of the wedge-shaped 

 bundles of wood through which the medullary rays passed are most 

 distinctly shown. They are long and narrow, and occur in an irre- 

 gular quincuncial order, as shown in my figure above named. 



2. As to the supposed vascular bundles dispersed throughout the 

 pith. Plate lY. fig. 2. represents a transverse section (natural size) 

 of the woody cylinder of Stigmaria, lately found by me in the middle 

 of a seam of coal in North Staffordshire. The specimen is highly 

 charged with iron pyrites, but it shows the characteristic reticulated 

 structure and medullary rays beautifully. The axis is filled with 

 eleven or twelve large vessels of a circular or oval form, each of 

 about one-tenth of an inch in diameter, having very thick walls*. 

 These vessels appear not to have been dispersed throughout the cel- 

 lular tissue, but lying contiguous to each other, whilst a small space 

 is left near the edge of the woody cylinder, as if resulting from 

 shrinkage. Their large size is very remarkable, far exceeding any- 

 thing of the kind that has come to my knowledge in fossil-plants. 

 Eig. 3 presents a longitudinal view, natural size, of these vessels, 

 and shows them to be elongated utricles ; and, although much larger 

 in size, of similar shape to those described by M. Brongniart as 

 occurring in the woody part of Sigillaria elegans. The pyritized 

 condition of the walls does not enable me to decide that these vessels 

 are marked by transverse striae on their different sides, but they 

 certainly have something like an appearance of that kind in the 

 arrangement of the pyrites. IN^o traces of the insertion of medullary 

 rays or bundles could be detected on the sides of the vessels. Alto- 

 gether these singular vessels remind me somewhat of the vascular 

 tissue in the middle of Anabaihra, and of an undescribed plant (in 

 my cabinet) allied to the genus Lepidodendron, except that the vessels 

 are much larger, and their walls much thicker. 



3. As to the structure of the rootlets of Stigmaria. In the 

 Memoir previously quoted. Dr. Hooker, at page 533, describes a spe- 

 cimen of a rootlet showing structure. He says, — ^' Por the highly 

 interesting specimen of a rootlet in which the cellular tissue is pre- 

 served, the Museum is indebted to Mr. Wariagton Smyth (Mining 

 Geologist to the Geological Survey). It is figured at pi. 2. fig. 1, 

 and consists of the silicified lower portion of a rootlet, the sides of 

 which have collapsed, so as to reduce its originally cylindrical form 

 to that of an irregularly four-sided prism. The substance is formed 

 of a network of exceedingly delicate cellular tissue (pi. 2. figs. 2 

 and 3), composed of hexagonal cells; and it is traversed through- 

 out its length by a dark line (fig. 2a), no doubt indicating the pro- 

 longation of one of those slender bundles of vascular tissue which 

 issue from the medullary rays of the axis (a of figs. 6 and 7), and 

 thence proceed to the mamillae on the surface of the specimen, 



* Some to whom this specimen has been shown regard these tubes as being 

 due to the mineralized condition of the central portion of the axis ; but I cer- 

 tainly consider them to be the representatives of the vascular tissue. 



