REVISION OF THE ENGLISH WEALDEN FLORA 



69 



Fig. 31 A-H Sulcalocladus robustus Watson & Harrison. A, B, C, unmacerated shoot fragments showing leaf-scars and decurrent leaf-bases separated by 

 sutures. Ai, V.64256; Aii, V.64257. Wealden, Duingen, North West Germany, x 2.5. B, C, two sides of same shoot from English Wealden at Worbarrow 

 Bay, Dorset. V.64589, x 5; D, cuticle of decurrent leaf-base with lower margin of leaf scar at top. V.64590. Galley Hill. East Sussex, x 25; E, cuticle of 

 decurrent leaf-base showing thinner cuticle of longitudinal sutures at each side. Indentation at top is lower part of leaf scar, V.64207, holotype. Wealden; 

 Duingen, North West Germany. LM, x 60; F, stoma on leaf-base cuticle surrounded by epidermal cells with pustules, V.64207, holotype. Wealden; 

 Duingen, North West Germany, LM, x 125; G, stoma viewed from inside showing cutinization of dorsal and ventral walls of guard cells, V.64291. Galley 

 Hill, East Sussex, SEM, x 750; H, outside view of stomatal pit, overhung by subsidiary cell papillae. V.64292, dispersed cuticle from Wealden; Duingen. 

 North West Germany, SEM, x 750, 



Yorkshire Jurassic and Mirovia szaferi Reymanowna (1985) from 

 the Jurassic of Poland. Manum (1987) suggested that nibbling by 

 insects might be the explanation in S. macrophylla. Harris (1979: 

 138) entertained the possibihty that the leaves of B. dura had a 

 hydathode at the tip which would be easily lost during fossilisation. 

 The expansion of the midrib in B. dura iust below the tip appeared to 

 support this but the vascular nature of the midrib has now been 

 questioned (Watson & Harrison 1998) though this needs further 

 investigation. Whatever the outcome for S. dura, there is no evidence 

 to support the presence of terminal hydathodes in S. greeboana (or in 

 P. linkii) and the lack of any insect damage elsewhere would appear 

 to make Manum's suggestion unlikely. In the absence of any evi- 

 dence to the contrary, it is suggested that the tips of the Wealden 

 leaves were susceptible to damage as they were shed from the tree 

 because they were very brittle, slender and probably scarious. The 

 particularly brittle nature of the cuticle of S. greeboana rather 

 supports this possibility. Reymanowna (1985: 7) noted that the 

 intact, slightly pointed tips in unmacerated leaves of Mirovia szaferi 

 lacked the lustre of the rest of the leaf and appeared to have much 



thinner cuticle which disappeared upon maceration. A thick, black 

 substance and swollen ends of resin ducts led her to suggest the 

 possibility of resin being secreted through the leaf apex. 



Genus SULCATOCLADUS Watson & Harrison 



1998 Sulcalocladus Watson & Harrison: 263. 



Diagnosis, [repeated from Watson & Harrison 1998] Shoots 

 clothed with spirally-arranged, narrow, elongate, decurrent leaf- 

 bases, each subtending a triangular foliage scar. Leaf-bases stomati- 

 ferous, separated by longitudinal, groove-like sutures. 



Type species. Abietites linkii (Romer) pro parte; emend. -Schenk 

 1871: 241, pL 39, fig, 6. 



Discussion. Sulcalocladus is a genus recently erected by Watson 

 & Harrison (1998) for coniferous shoots which consist largely of 

 decurrent leaf-bases subtending leaf-scars, probably of deciduous 

 leaves. Of the two distinct species identified so far, the one described 



