354 
KIDSTON : THE FLORA OF THE CARBONIFEROUS PERIOD. 
(jnly separated by a very narrow space. The lateral angles of the 
alternate leaf-scars project slightly and impart to the furrows a more 
or less zig-zag course (Sigillaria elegans Sternb. sp., Plate LVIIL, 
fig. 3). The cone scars form a verticel round the stem. 
The chief distinguishing character of this section is the close leaf- 
scars and zig-zag furrows. 
Section III. — Clathraria Brongniart. 
Stems without ribs with leaves placed on contiguous, slightly 
elevated, rhomboidal cushions, which are separated by deep oblique 
furrows. Cone scars forming irregular verticils and placed in the 
furrows between the leaf-cushions, or in two opposite vertical rows. 
Typical form, Sigillaria Brardii Brongt. (Plate LVIIL, fig. 2). 
Section IV. — Leiodermaria Goldenberg. 
Stems without ribs having distant leaf-scars without cushions. 
Surface of bark between the leaf-scars variously ornamented, often 
with fine longitudinal, flexuous strise, which are frequently cross- 
hatched with delicate lines {Sigillaria camptotoenia Wood sp., Plate 
LXL, fig. 2). The cone scars form irregular broad verticils. 
The Rhytidolepis and Favularia sections pass into each other, 
and only in a very few species can the distinction be observed. 
Any interfoliar space on the surface of the ribs is seldom or never 
entirely free from some ornamentation in the form of transverse lines 
or small irregular punctations, especially immediately above and below 
the leaf-scar. Sometimes these ornamentations are very prominent 
and form a distinct central band connecting the leaf-scars (Sigillaria 
rugosa Brongt., Plate LXL, fig. 1). A slightly raised line generally 
descends from the lateral angles, occasionally extending to the lower 
leaf-scar and forming the limit of the central band of ornamentation. 
The two sections Clathraria and Leiodermaria also pass into 
each other ; in fact, they occur on the same specimen (Plate LIX., fig. 1), 
and thus appear to be only conditions of growth. The distance or 
approximation of the leaf-scar cannot always be regarded as a specific 
mark, for even in the ribbed Sigillariae, with normally distant leaf- 
scars, specimens are occasionally found on which, apparently from 
