534 MR ROBERT KIDSTON ON 
In the same manner, groups III. and IV. run into each other; and though some 
species appear to possess only the characters of the Clathrarie, as Sigillaria discophora, 
Konig, sp. (= Ulodendron minus, L. & H.), and others those of the Levodermarie, as 
Sigillaria camptotenia, Wood, sp., still typical specimens of the groups Clathraria 
(Sigillaria Brardi, Brongt.) and Lewodermaria (Sigillaria spinulosa, Rost, sp.) have 
been found more than once organically united on the same example.* 
A transition from the Clathraria to the Favularva can also be seen in Sigillaria 
semipulvinata, Kidston.t 
It is therefore evident that, although the outer surface of the stems of Sigillaria 
differs in being ribbed or smooth, and in the leaf scars being distant or approximate, 
all these forms are closely connected by intermediate links; and though the larger 
division of ribbed and non-ribbed stems is generally very distinctive, still a case is not 
wanting to show how closely even these two groups stand to each other. 
There are, however, differences in the structure of the vascular system of those 
stems of Sigzllarza whose internal organisation is known, and though these differences 
are only variations of a single type of structure; they may hold a definite relation 
to the group of which the species is a member ; so it is not without interest to consider 
this point in connection with the group to which the species belongs. Stems of 
Sigillamva showing their internal structure and the outer surface of the bark, and 
thus permitting of a specific determination, are, however, very rare. 
The earliest description of the internal structure of Sigularia is that given by 
BRONGNIART in his well-known memoir, ‘“‘ Observations sur la structure intérieur du 
Sigillaria elegans comparée a celle des Lepidodendron et des Stigmaria et a celle 
du végétaux vivants.” { It is rather remarkable, however, that the plant Broneniart 
identified as Sigularia elegans in this memoir is, as ZEILLER§ has pointed out, — 
the Sigillaria Menardi, Bronet.,|| and therefore a member of the Clathrarian 
section. 
In 1872 Wituiamson described some Sigillarian remains which he referred to 
Favularia, but his specimens were very imperfect, and threw little additional 
light on the subject.4] 
It was not till the publication of RenauLt and Granp’ Eury’s memoir, “ Etude sur 
*Wuiss, Zeitsch. d. deut. geol. Gesell., 1888, p. 566. ZEILLER, Bull. Soc. géol. d. France, 3° sér., vol. xvii. p. 608, pl. 
Xiv., 1889. ZEILLER, Flore fossile, Bassin houiller et permien de Brive, p. 88, pl. xiv. fig. 1, 1892. Kinston, Proc. 
Roy. Phys. Soc. Edin., vol. xiii. p. 233, pl. vii. fig. 1, 1896. 
+ Trans. Roy. Soc. Edin., vol. xxxix. p. 57, pl. ili. figs. 1-5, especially figs. 1, 2, 1897. 
t Archives du Muséum, vol. i. p. 405, pls. xxv.-xxviii., 1839, Paris. See also Renavtt, “Structure comparée de 
quelques tiges de la flore carbonifere,” Nouvelles Archives du Muséum, ii., 2° sér., 1879, p. 262, pl. xi. fig 13. RenavLt, 
Flore fossile, Deux. part, Bassin howiller et permien d’Autun et d’Epinac, fase. iv. p. 200, pl. xxxvi. figs. 8-11, pl. xxxvii. 
figs. 3-7, 1896. 
§ Ann. d. Screnc. nat., 6° sér., Bot., vol. xix. p. 259, 1884. Wauuss, Sitz. Bericht. d. Gessell. naturforsch. Freunde zu 
Berlin, 1886, No. 5, p. 70. 
|| Hist. d. végét. foss., pl. clviii. fig. 6 ( ? non fig. 5). 
J “On the Organisation of the Fossil Plants of the Coal Measures.” Part II. Lycopodiaceze : Lepidodendra and 
Sigillarie. Phil. Trans., 1872, p. 197. 
