of the Fossil Plants of the genus Sigillaria. 127 
cular tissue is ever found in the medullary rays, unless those curious 
plates described by Griffith in the wood of Phytocrene gigantea, in which 
vessels exist, should prove to belong to the medullary system.”* Should 
botanists agree to restrict the term medullary ray to those vertical plates 
of cellular tissue which intersect the ligneous cylinder, and which are 
unaccompanied with vascular tissue, the radiating plates of Stigmaria 
cannot be so termed, as they inclose the vascular cords which pass into 
the external appendages. 
By making longitudinal divisions through the cylinder of those speci- 
mens of Stigmaria which do not possess 
any tissue, we discover that the radiating Fig. 1. 
plates are about half an inch in length in A 
_ the longitudinal direction of the fossil ; ) 
that they are placed rather obliquely, and V 
disposed in a nearly spiral manner ; and 
that they thin off at one end to a fine 
edge, while the opposite one is divided, or 
rather grooved, along its entire horizontal 
extent. Ihave endeavoured to represent the form of a plate, and a 
groove in the annexed figures :—t 
Referring to Brongniart’s section of Stigmaria, we learn that the cylinder 
is intersected by a number of oval-shaped spaces, each of which in- 
closes the vascular bundle or cord belonging to one of the external ap- 
pendages or fibrils.t| Mr Morris’ figure, representing an oblique section 
of the same part at right angles to the radiating plates, shews similar 
oval-shaped spaces inclosing a cord.§ Now, if in imagination we de- 
stroy the whole of the tissue, and fill up the oval-shaped spaces of these 
figures with mineral matter, we produce a number of radiating plates, 
with a groove precisely like those which have been figured. This brief 
notice is perhaps sufficient to shew that the radiating plates were origi- 
* Introduction to Botany. 3d edit. p. 92. 
t Fig. 2 represents a side view of a plate having one of the divisions removed, 
to shew that the groove deepens as we pass from 
the inner (a), to the outer side (6). Figure 1 re- 
presents a longitudinal section of another plate cor- 
responding to the dotted line in figure 2. 
} “ Observations,” &c., Plate V., figs. 2, 6, and 7. 
In the annexed figure, which is a reduced copy of fi- 
gure 6, one of the spaces (a) surrounded with tu- 
bular tissue, (4) is represented as well as the bundle 
(c.) 
§ Geological Transactions, 2d series, vol. 5, Plate 
XXXVIII. fig. 3, a. 
