REVISION OF THE ENGLISH WEALDEN FLORA 



(Figs lOE, F; HE, H) and has guard cells with strongly cutinized 

 dorsal plates (Figs lOF; 1 ID, H) forming the floor of the stomatal pit. 

 The guard cells are also thickly cutinized along the part of the inner 

 anticlinal wall adjacent to the stomatal opening and extending onto 

 the inner periclinal walls. This thickening makes the stomatal slit 

 particularly prominent in both the light microscope (Figs. 1 OE; 1 1 E) 

 and the SEM (Figs. lOF; IID, H). The guard cells are sunken 

 beneath, and overlapped by. usually 6 subsidiary cells with thickened 

 inner anticlinal walls (Fig. 1 IE) forming the rim of the stomatal pit 

 which might or might not bear overhanging papillae. 



The upper cuticle of the leaf in Fig. 10 shows the slightly elongate 

 ordinary epidermal cells arranged in longitudinal rows (Fig. lOA, B). 

 The outer surface is generally smooth, but small patches of longitu- 

 dinal ridges are seen on some specimens (Fig. IOC). The stomata are 

 scattered and mostly longitudinally orientated (Figs 8G; lOA, B). 

 The stomatal pits are typically more slit-like (Fig. lOD) than the 

 stomata of the lower cuticle (Fig. lOE, F) but are otherwise similar, 

 sometimes with papillae developed around the pit rim (Fig. lOA). 



The lower cuticle (Fig. 1 1 A-H) shows more isodiametric ordi- 

 nary epidermal cells with tracts of slightly elongate cells, probably 

 over the veins, arranged in longitudinal files (Fig. 11 A, C). The 

 relatively smooth outer surface is seen in Fig. 1 IB with the pits of the 

 scattered and randomly orientated stomata (Figs 8H; 1 1 A, C) more 

 or less level with the surface. The oval pit rims bear varying numbers 

 of subsidiary cell papillae overhanging the pit. In some stomata each 

 subsidiary cell is papillate (Fig. 1 1 F), others have one or two subsidi- 

 ary cell papillae (Fig. HE) and in some stomata this feature is 

 scarcely developed at all (Fig. 11 G). 



The presence of numerous round and occasionally spindle-shaped 

 resin bodies in both leaf and petiole specimens is revealed by 

 maceration (Figs 7 A, C, G; 9B). Isolated pieces of amber are also 

 quite common in many of the debris beds processed during this study 

 and further studies of these and other Wealden resins are underway 

 using organic geochemical methods (Gize, pers. comm. 2000). 



A female reproductive structure discovered adhering to the cuticle 

 of a leaf segment of G. weatherwaxiae. and possibly attributable to 

 it, is discussed and described below. 



Comparison. A single comparison of all the three species of 

 Ginkgoites found in the English Wealden, and described in the 

 present work, is given below, together with comments on species of 

 Ginkgoites from Lower Cretaceous floras elsewhere. 



Ginkgoites nannyoggiae sp. nov. 



Figs 12-15 



Diagnosis, [based on leaf fragments only] Lobes of deeply di- 

 vided lamina up to at least 1 mm wide and 20 mm long with rounded 

 apices. Circular resin bodies frequent, up to 3 per mm^, 100-200 |im 

 in diameter. Veins parallel and dichotomising, 250-600 |am apart, up 

 to at least 1 2 per leaf segment. 



Cuticle of both surfaces very thick; anticlinal cell walls straight; 

 anticlinal and periclinal walls often strongly pitted. Upper cuticle 

 usually lacking stomata, rarely with I per 2 or 3 mm^, stomatal 

 apparatus as for lower cuticle except indistinct and papillae absent. 

 Ordinary epidermal cells polygonal, 4-5 sided, isodiametric, 



45 



occasionally arranged in longitudinal files, average cell-size 25 (10- 

 40) \xm. Trichomes and papillae absent. 



Lower cuticle with scattered stomata usually avoiding veins; 

 average density 69 per mm^, randomly orientated. Stomatal appara- 

 tus elliptical in outline, typically 75 (44-125) \xm long and 64 

 (44-84) |jm wide; guard cells with narrow dorsal plates slightly 

 sunken beneath ring of 4-7, usually 6, .subsidiary cells each with 

 hollow papilla overhanging oval stomatal pit. Ordinary epidermal 

 cells of lower surface polygonal, 4-5 sided, averaging 28 (10-57) 

 |jm long and 23 ( 14-37) pm wide, randomly arranged or in longitu- 

 dinal files; anticlinal walls straight; outer ordinary epidermal cells 

 each with bulging outer periclinal wall bearing a large, hollow 

 papilla. 



Name. After Nanny Ogg, matriarch and witch of Lancre in the 

 Discworld novels of Terry Pratchett. 



HOLOTYPE AND TYPE LOCALITY. V.64545, Fig. 12C, a dispersed 

 leaf fragment from Galley Hill, Ea.st Sussex, locality 51 BH of 

 Oldham (1976). Ashdown Beds Formation; Berriasian. 



Material and occurrence. Specimens of Ginkgoites nanny- 

 oggiae sp. nov. have been found only as dispersed fragments, with 

 good cuticle preservation, within the plant debris beds of the English 

 Wealden. Although the holotype was contained in a sample collected 

 by Oldham (1976) from the Sussex Wealden, most of the material 

 has been found in the younger beds of the Wessex Formation in 

 Dorset, at Worbarrow Bay and Mupe Bay. Figs 12A, B, G; 1 5 A, E 

 show material from Worbarrow Bay. Figs 12D-F; I4D; 15B,Dshow 

 material from Mupe Bay. Figs I2C; 13A-C; 14A-C; 15C, F show 

 the holotype from Galley Hill, East Sussex. Stratigraphical range: 

 Berriasian - Hauterivian. 



Description and discussion. The largest leaf fragments recog- 

 nized so far show that Ginkgoites nannyoggiae sp. nov. had segments 

 up to at least 10 mm wide with rounded apices (Fig. 12A-C). At 

 present there is no evidence on which a whole leaf can be recon- 

 structed nor is it known whether the leaf was petiolate. Numerous 

 resin bodies are a prominent feature of this species throughout all the 

 known leaf segments (Fig. I2C, G). They are revealed by maceration 

 but the flattened discs of resin are loosened in the process and they 

 easily dissipate with subsequent handling of the leaf 



The upper cuticle of G. nannyoggiae {¥\gs 12E-G; 13B; 14A-C) 

 shows isodiametric ordinary epidermal cells arranged either ran- 

 domly (Fig. 12G) or in longitudinal files (Fig. 12F). Figs 12G and 

 148 show the heavily pitted appearance of both the anticlinal and 

 periclinal walls. An interesting feature of the outermost surface of 

 the upper cuticle is the presence, on some specimens, of sparsely 

 scattered oval scars. In the light microscope these scars can be seen 

 to overlap 2-3 ordinary epidermal cells (Fig. 14A) and the SEM 

 reveals them to be simple rimmed depressions (Fig. 14C). It seems 

 most likely that they are the bases of thinly cutinized trichomes 

 which were either shed in life or subsequently lost during fragmen- 

 tation of the leaf. The adaxial outer surface is otherwise rather 

 smooth and featureless (Fig. 12E). 



The cuticle of the lower surface (Figs 12D; 13A.C; 14D; I5A-F) 



Fig. 11 A-H Ginkgoites weatherwaxiae sp. nov. All cuticle of lower surface of leaf. A, stomatal distribution and arrangement of ordinary epidermal cells, 

 V.64539, LM, x 125; B, relatively smooth outer surface of cuticle showing stomatal pits level with general surface. V.64542. SEM, x 125; C, inner 

 surface of cuticle showing scattered stomata, V.64542, SEM, x 125; D, 3 stomata viewed from inside, showing variable orientation V.64542, SEM. x 500; 

 E, single stoma with prominent stomatal slit, thickening around pit rim, thickening extending along radial anticlinal walls of the subsidiary cells and 

 papillae overhanging stomatal pit, V.64539. LM. x 500; F, highly papillate stoma viewed from outside, one large papilla on each subsidiary cell. V.64532, 

 SEM, X 750; G, non-papillate stoma viewed from outside showing upper surface of guard cells and stomatal slit. V.64542, SEM, x 750; H, single stoma 

 viewed from inside showing guard cells with thickly cutinized semi-circular dorsal plates and thickened inner anticlinal walls, V.64542. SEM, x 750. 



