126 



FOSSIL PLANTS. 



" The broad space intervening between the internal and external radiating cylinders, 

 filled with lax cellular tissue and traversed by medullary bundles communicating with 

 the leaves on the outside of the stem, as shown in the specimens described in this paper, 

 is the only part on which information is required to complete our knowledge of the 

 structure of the stem of Sigillaria. Fortunately a small specimen of 

 ^" Sigillaria vascularis, kindly presented to me by Mr. Ward, of Long- 



ton, a most indefatigable collector, has enabled me to obtain con- 

 siderable information on this point. This specimen shows the rhom- 

 boidal scars on the outside of the stem, the two radiating cylinders, 

 and the space between occupied by lax cellular tissue and traversed 

 by medullary bundles. 



" The specimen in this woodcut^ (fig. 5 [fig. 4], magnified twice) 

 is of smaller size than any previously described by me, but it is, from 

 both its internal structure and external characters, a small Sigillaria 

 vascularis in its young state, when the two radiating cylinders, espe- 

 cially the outer one, of the plant were only slightly developed. The 

 medullary rays are seen on the outside of the inner radiating cylinder, 

 and pass, inclining upwards at a small angle, from the inner cylinder 

 to nearly the outside of the stem. No trace of the outer cylinder 

 can be seen, so as to enable us to see whether the smaller-sized 

 medullary bundles, coming from the inner cylinder, join the larger 

 ones in the outer cylinder, described in pi. xxxiv, fig. 2, and there 

 marked d' . All the .tangential sections show the medullary bun- 

 dles, both in large and small specimens, to be much greater and 



Sigillaria vascularis. ° _ _ ... 



stronger in the outer than in the inner radiating cylinder ; but no 

 evidence has yet been found of the junction of these medullary bundles to prove that 

 the former run into the latter, or whether the two are distinct. They consist of hexagonal 

 tubes, barred on all their sides, surrounded by muriform tissue, that on the outside 

 of the specimen being of very coarse texture."^ 



1 Obligingly lent by the Council of the Royal Society. 



2 In all the large and small specimens of Sigillaria vascularis which have come under my observation 

 that illustrated by this woodcut is the only one that clearly shows the vascular or foliar bundles proceeding 

 direct from the outside of the inner radiating cylinder to the leaf-scars. This, from recent investigations, 

 has been known to be the case. On its outside it is covered with rhomboidal scars like all the small 

 specimens. The space intervening between the inner radiating cylinder and the outer one appears to have 

 once consisted of iron-pyrites, which has since been decomposed, leaving the vascular or foliar bundles 

 fully exposed. On comparing the direction which these organs take, from the inner to the outer 

 radiating cylinder, with those shown in the specimen " No. 31," Plate XIII, figs. 2 and 3, of Lepidodendron 

 Harcourtii in this Monograph, it will be seen that they run in nearly a horizontal direction, compared with 

 the high angle the latter make when proceeding from the stem. This difference in the direction of the 

 vascular or foliar bundles in Lepidodendron and Sigillaria vascularis is very marked, and worthy of the 

 attention of those authors who contend that the latter plant is only a Lepidodendron. — E. W. B. 



