of the Fossil Plants of the genus Sigillaria. 13 



a structure analogous to that of Sigillaria elegans. However, in the pre- 

 sent state of our knowledge, a much more striking analogy exists as to 

 their internal structure between the fossil and some Cycadacece. 



'* This analogy is particularly striking between Stigmaria and Zamia 

 integri/olia ; but, on the other hand, the difference in the external form, 

 both as it regards the stem and the leaves, is very great ; and as to 

 Sigillaria^ of which the leaves are unknown, and of which the stems 

 have often, by their external characters, more resemblance to those of 

 the Cycases, it may be objected, \st, The presence of its medullary sheath 

 formed of large bundles, of which no traces are to be found in any of the 

 latter plants ; 2(?, The absence in the coal-formation of leaves analogous 

 to those of existing Cycadarece. 



" All these considerations lead to the conclusion, that Sigillaria and 

 Stigmaria constitute a peculiar and extinct family belonging probably 

 to the Gymnospermous division of the Dicotyledons, but of which neither 

 the fruit nor the leaves are as yet known. These fossils, it is evident, 

 are clearly related to each other, and Anabathra ought likewise to form 

 a part of the same group. Perhaps Stigmaria is only the root of Sigilla- 

 ria. The uniformity of the external characters observable on specimens of 

 the first of these genera would then correspond to the trifling variety of 

 form required in roots belonging to various species ; further, the creep- 

 ing habit of this fossil, and the form of its scars, agree very well with 

 this supposition ; against which, however, may be urged the regularity 

 of the quill cuncial arrangement of the appendages (or fibrils ?), a regularity 

 which has, nevertheless, been found in the roots of some aquatic plants. 



" This supposition will explain the origin of the singular dome-shaped 

 specimens which have been described by Messrs Lindley and Hutton in 

 the '' Fossil Flora," and from which branch out, in a radiating and hori- 

 zontally creeping manner, the dichotomous stems of Stigmaria. The pre- 

 sence of a pith in the centre of the ligneous cylinder of the fossil is not a 

 very serious objection, for I have ascertained that the roots of several 

 Zamice possess a perfectly distinct and rather voluminous pith ; this struc- 

 ture is particularly apparent in the roots of Zamia pvngens, the tissue of 

 ■which displays, though on a smaller scale, an arrangement very analo- 

 gous to what is observable in Stigmaria." 



Before concluding with Brongniart as to the situation of Sigillaria in 

 the vegetable kingdom from its internal structure, it will be necessary 

 to examine some other characters of this genus, and also to consider 

 some plants of the same geological age, and others which are now liv- 

 ing ; for I hope to be able to shew that considerations of this kind will 

 materially affect the conclusion in question. 



Within the last three years the collection of fossil plants in the New- 

 castle Museum has been enriched with two nearly complete stems of the 

 so-called Sigillaria reniformis in a decorticated state. Both specimens,* 



* For these specimens the Society, in whose Museum they are placed, is in- 

 debted to the liberality of the Messrs Fauton. Kirk, and partners. 



