REVISION OF THE ENGLISH WEALDEN FLORA 



the shoots from which the leaves were shed and Fig. 32 shows 

 reconstructions of them bearing the two leaf forms of Pseiidotorellia 



linkii. 



Pseudotorellia vimesiana sp. nov. Figs 24. 25 



1969 Unnamed conifer, Magdefrau & Rudolf: 297, text-tlg.6. 

 [Wealden, North West Germany]. 



Diagnosis. Leaf parallel sided for much of its length; up to at least 

 17 mm long, 0.5-1.7 mm wide; tapering to acute apex; base shortly 

 attenuate. 2 resin canals present in some leaves. [Veins not dis- 

 cerned.] 



Cuticles about 10 |um thick; upper usually slightly thicker than 

 lower. Upper cuticle without stomata. Upper epidermal cells arranged 

 in longitudinal files, rectangular or square; late division pairs of cells 

 common. Cells 35-170 |jm long (mean length 87 \xm)\ divided cells 

 generally 8-27 \xm wide (mode 17 |jm); ordinary cells 30-65 pm 

 wide (mode 38 pm). Anticlinal walls generally 3-12 pm wide, 

 becoming wider near leaf-base; straight or slightly undulating; fre- 

 quently pitted. Surface walls flat and of uniform thickness; finely 

 pitted on outside or longitudinally striated, striations not restricted to 

 one cell. Papillae and trichomes absent. Hypodermis usually present. 

 Hypodermal cells arranged in longitudinal files; square or rectangu- 

 lar and elongated transversely, occasionally triangular; 40-1 15 pm 

 long (mean length 65 pm) x 50-1 15 pm wide (mean width 78 pm). 



Lower cuticle with stomata arranged in 2 or 3 bands near leaf- 

 base, merging to a single broad band distally. Stomatal density inside 

 bands 50-1 1 per mm- ( mean density 73 per mm'). Ordinary epider- 

 mal cells arranged in longitudinal files; files may or may not be 

 slightly disrupted in stomatal bands. Cells between stomatal bands 

 rectangular, 45-190 pm long (mean length 123 pm) x 15-30 pm 

 wide (mean width 22 pm). Cells within stomatal bands 3, 4 or 5- 

 sided, elongated longitudinally or isodiametric or, very occasionally, 

 wider than long; 20-130 pm long (mean length 63 pm) x 20-60 pm 

 wide (mean width 29 pm). Longitudinal bars rare. Anticlinal walls 

 3-8 pm wide, becoming wider near leaf base; straight or slightly 

 undulating; occasionally pitted. Outer periclinal walls usually flat 

 and of uniform thickness, rarely with faint median longitudinal ridge 

 on outside; outer surface finely pitted or, on some leaves, striated. 

 Striations longitudinally aligned, not restricted to one cell. Papillae 

 and trichomes absent. Hypodermis frequently present beneath ordi- 

 nary epidermal cells, absent beneath stomatal apparatus. Hypodermal 

 cells arranged in longitudinal files, generally square or rectangular 

 and elongated transversely, usually 45-65 pm long x 35-70 pm 

 wide. 



Stomata longitudinally orientated. Stomatal apparatus 68- 1 52 pm 

 long (mean length 104 pm) x 45-95 pm wide (mean width 73 pm). 

 Stomatal pit with smooth oval rim. Inner anticlinal walls of subsidi- 

 ary cells broad, inwardly sloping to form crater-like pit with small 

 hole at base. Subsidiary cells arranged in a ring around the pit; 2 polar 

 and 2, 4 or rarely 6 lateral; none bearing papillae. Encircling cells 

 occasionally present laterally. Guard cell pair slightly sunken be- 

 neath subsidiary cells; 38-80 pm long (mean length 57 pm) x 27-65 

 pm wide (mean width 38 pm); dorsal plates thickly cutinized, axe- 

 head shaped; T-pieces thinly cutinized; ventral walls not preserved 

 or sometimes thinly cutinized. 



Name. After Sir Samuel Vimes, commander of the Ankh-Morpork 

 City Watch in the Discworld novels of Terry Pratchett. 



HOLOTYPE & TYPE LOCALITY. V.64555, Fig. 24B, a leaf from 

 debris beds in the Wessex Formation at Mupe Bay. Dorset. Wessex 

 Formation, Barremian. 



61 



Material & occurrence. The species is known in dispersed 

 material from the Ashdown Beds Formation at Hastings, the Wessex 

 Formation at Mupe Bay in Dorset and the Wealden leaf coal of 

 Diiingen, North West Germany. It has also been recognised amongst 

 the NHM Seward collection from the Lower Cretaceous of Western 

 Greenland. 



Description. The leaves of Pseudotorellia vimesiana sp. nov. are 

 some of the smallest assigned to the genus Pseudotorellia. They 

 appear to have been needle-like in form with slightly constricted 

 bases and, according to Miigdefiau & Rudolf (1969: 297), have 

 sharply pointed apices. Two unbranched resin canals have been 

 recognised in some leaf fragments from Western Greenland (Fig. 

 25 A, B), one running close to each lateral margin and avoiding the 

 stomata arranged in a single band. Other more complete leaves 

 described below reveal that the stomata are arranged in two or three 

 bands near the leaf base, merging into one in the more distal regions. 

 Some of the leaves exhibit a faint differentiation of the upper 

 epidermal cells along the midline. These cells are narrower and more 

 elongate than usual. The rectangular outline of all the upper epider- 

 mal cells and their arrangement in longitudinal files is shown in Figs 

 24L and 25D. The latter also illustrates the high proportion of cells 

 which are split into pairs by late cell division. Each member of the 

 pair is about half the width of most other cells and the paired cells 

 generally having a width between 8 and 27 pm, the most common 

 value being 17 pm; the unpaired cells being 30-65 pm wide with a 

 width of 38 pm recorded most frequently. 



The anticlinal walls of the epidermal cells are frequently traversed 

 by straight pits seen in Fig. 25D which also shows the finely 

 cutinized outlines of the larger, transversely elongate, hypodermal 

 cells. Such cutinization is only irregularly developed and inner 

 periclinal cutinization of the epidermal cells is very rare. Fig. 24J 

 shows the generally flat outer periclinal walls of the epidermal cells, 

 which are of uniform thickness. 



Fig. 24B, D shows that, as in all species of Pseudotorellia, the 

 stomata of P. vimesiana are restricted to the lower leaf surface where 

 they are always orientated longitudinally. Fig. 24D also shows the 

 stomata arranged in three bands at the leaf base. They do however, 

 gradually merge into a single broad band in the distal part of the leaf. 

 The margins of the bands are characteristically indistinct in Fig. 

 24D; although the ordinary lower epidermal cells have a tendency to 

 be shorter and wider within the stomatal bands than between them, 

 the change is not an abrupt one. The ordinary cells near the leaf base 

 on both surfaces are considerably smaller, more square and have far 

 thicker anticlinal walls than those elsewhere (as in Pseudotorellia 

 linkii). Fig. 24J, K shows the finely pitted outside surface of the 

 cuticle, but in some cuticles (e.g. Fig. 25C) this pitting is replaced by 

 longitudinal striae. The hypodermal cutinization which is frequently 

 present beneath the epidermal layer is shown in Fig. 24F. The 

 stomata off! vimesiana are small and quite closely packed together 

 (Fig. 24B-E). The thickly cutinized dorsal plates make the stomata 

 conspicuous in the light microscope (Figs 24C, G, H; 25E, F) and 

 from the inside in the SEM (Fig. 24E, F, I), but from the outside in the 

 SEM they are quite inconspicuous (Fig. 24J, K). the stomatal pits 

 being crater-like (Fig. 24K) and lacking a distinct rim. The inwardly 

 sloping walls converge towards the little hole at the bottom of the pit. 

 which is shown most clearly in Fig. 25F. This figure also shows that 

 the wide inner anticlinal walls of the lateral subsidiary cells may 

 easily be confused in the light microscope with the dorsal plates of 

 the guard cells which underlie them. The dorsal plates are generally 

 wider than the inner anticlinal walls of the subsidiary cells so that 

 only the guard cell thickenings can be .seen on the inside of the cuticle 

 with the SEM (Fig. 241). The party wall between the guard cell pair 



