SIGILLAKIA. 173 



A definite limit of the leaf-cushion often absent (Leioderman'a), 

 occasionally incomplete, or distinct ( Clathraria). Leaf-cushion, 

 when present, more or less elevated, generally rounded above and 

 below, or subquadrate or spathulate with truncated base, and 

 generally without any surface ornamentation. Leaf-scar usually 

 on the upper portion of the cushion, central only in the young 

 condition. In the Leiodermarian forms the outer surface of the 

 bark, between the leaf-scars, is generally ornamented with a 

 shagreen-like sculpturing of fine longitudinal ridges and delicate 

 transverse stria?. The longitudinal lines are longer and coarser 

 than the fine transverse striae ; under the leaf-scar the bark is 

 frequently smooth — above the leaf-scar it is generally smooth. 



Immediately beneath the leaf-scar on certain Leiodermarian 

 forms there sometimes occur one or two small circular scars. 

 Cortex thin— decorticated stem longitudinally striated. The cone- 

 scars form an irregular girdle round the stem. They are small, 

 circular, oval, or subtriangular, and in the Clathrarian forms are 

 placed on small cushions inserted between the leaf-scars, which, 

 like the cone-scars, are usually more or less deformed by mutual 

 pressure. In the Leiodermarian forms they possess no cushion, 

 and are circular from the absence of all pressure. The internal 

 anatomy of the stem has the characters described above under 

 the genus. 



Mr. Kidston 1 published some years ago a full account of this 

 species and its variations, from which the above description, with 

 the exception of a few verbal alterations and additions, is taken. 

 He has confirmed the conclusion that S. Menardi, Lrong., 

 S. spinulosa, Germar, and S. denudata, Giipp., are merely 

 varieties of S. firardi, Brong. 



The internal anatomy of at least two varieties of S. Brardi is 

 known, but as the South African specimens described below are 

 not petrified, the structure of the stem need not be dealt with in 

 detail here. 2 



1 Kidston (96) ; see also the papers by Zeiller (89), Weiss & Sterzel (93), 

 Seward (90) mentioned above. 



• For a full account of the anatomy of S. Brardi see the memoirs by 

 Brongniart (39), Renault & Grand'Eury (75), Corda ^45), & Scott (00) given hi 

 the list of synonyms. 



