REVISION OF THE ENGLISH WEALDEN FLORA 



conifer Elatides williamsoni Harris. In this species, tiie megaspore 

 membrane is combined with what Harris called the 'outer cell-layer 

 of the endosperm" (Harris 1943: 332). This consists of large, brown, 

 straight-walled isodiametric cells, occasionally incompletely filled 

 and represented by more or less isolated globular masses. Harris 

 interpreted these as the oily food reserves of the prothallus which 

 have been converted into a resistant mass of resin (Hanis 1943, 

 1954). It is evident that a fairly unusual mode of preservation has 

 occurred and that more specimens will need to be found and studied 

 in order to improve our understanding of this structure. 



Two pollen grains can be seen within the pollen chamber formed 

 by the nucellar beak (Figs 20G: 21) using the light microscope, 

 although they are obscured by both cuticular layers. A median colpus 

 can be recognised on one of the pair (Fig. 21). Monocolpate pollen 

 has been found within, and closely associated with, other fossil 

 ginkgoalean ovules (Krassilov 1972; Harris & Millington 1974; 

 Zhou & Zhang 1989, 1992), but it is associated with various gymno- 

 sperm groups, including the Ginkgoales, Cycadales and Bennettitales 

 (Batten 1974) and any speculations as to affinity, based on two 

 partially obscured grains of pollen from a single ovule are, at best, 

 inconclusive. 



Comparison. The ovule attributed to Ginkgoites weatherwaxiae 

 can be compared to previously described ginkgoalean female repro- 

 ducfive structures. Zhou (1997) presented a review of Mesozoic 

 ginkgoalean genera, of which Allicospermiim Harris, Karkenia 

 Archangelsky, Yimaia Zhou et Zhang and fossils referred to Ginkgo 

 L. are of relevance here. All of these share the same basic structure: 

 an orthotropous ovule with a thick megaspore membrane, a thin 

 nucellar cuticle and an integument, with an inner and an outer 

 cuticle, showing well-developed fieshy and stony layers. 



Allicospermum is a form-genus of broad scope which may well 

 include seeds of various plant groups, including the Ginkgoales, 

 Cycadales and Coniferales. Several species are believed to be ihe 

 seeds of fossil ginkgoaleans, including the type species, A. xystum 

 Harris, from the Lower Jurassic of East Greenland (Harris 1935), 

 which is attributed to the leaf species Ginkgoites taeniata (Braun) 

 Harris. These seeds tend to be much larger than the ovule described 

 here. The other three genera differ in the size, number and arrange- 

 ment of ovules in the ovule-bearing organ: fossils attributed to 

 Ginkgo bear 2-3 large orthotropous ovules attached to a peduncle, 

 Yimaia is a form-genus for clusters of sessile ovules borne on the end 

 of a peduncle (Zhou & Zhang 1992) and the genus Karkenia was 

 erected for organs bearing many small pedunculate ovules on a 

 central axis (Archangelsky 1965). The ovules of Ginkgo and Yimaia 

 are generally large and Karkenia, though considerably smaller, bears 

 ovules about three times the size of that attributed to G. 

 weatherwaxiae. 



Evidence of the nature of the integument is entirely lacking, as is 

 that of the structure of the ovule-bearing organ, and we feel it would 

 be inappropriate to place the ovule described here within any of these 

 genera, even though shared similarity in structure is clear. 



Comparisons can also be made with Spermatites. a genus erected 

 by Miner (1935) for small hollow cuticular structures from the 

 Upper Cretaceous of Western Greenland. He was unsure as to their 

 affinity and employed Spermatites "as a convenient designation for 

 such unassigned organs" (Miner 1935: 597), although he did recog- 

 nise that they probably represented seeds. The majority of species 

 are of late Early to Late Cretaceous age (Batten & Zavattieri 1995) 

 and may represent the seed coats of close relafives of the extant rush 

 genus yM«cM5(Binda&Nambudiri 1983; Batten & Zavattieri 1996). 

 However, older species attributed to this genus appear to be of 

 gymnospermous origin and Batten & Zavattieri suggested that it 



55 



should be regarded as a 'heterogeneous taxon that includes repre- 

 sentatives of a variety of plant groups" (Batten & Zavattieri 1 995: 77). 



Spermatites pettensis Hughes, from the Ashdown Beds Formation 

 of the English Wealden (Hughes 1961 ), is a seed of the same size and 

 general morphology as the ovule described here. Cuticle described 

 by Oldham (1976) as 29 Gink GkC and now known to be G. 

 weathenraxiae occurs in the same beds as S. pettensis. Hughes 

 interpreted the structure as a gymnospermous ovule consisting of a 

 thick, punctate nucellar cuticle forming a well developed pollen 

 chamber, covered in its upper half by thin inner integument cuticle 

 which continued into a long micropylar tube. He also noted the 

 presence of Eiicommiidites pollen in the micropylar tube and the 

 pollen chamber. 5. pettensis was subsequently reinterpreted by 

 Reymanowna (1968) in accordance with her description of Polish 

 £((co/w)/(/V/;7e,s-containing specimens of Allicospermuni retemirum 

 Harris, a seed species originally described from the Middle Jurassic 

 of Yorkshire (Harris 1944). She observed that although /^. retemirum 

 is about five times larger than S. pettensis, the cuticles present are 

 virtually the same: a thick megaspore membrane and a nucellar 

 cuticle with an extended micropylar tube. This interpretation of the 

 cuticles present in S. pettensis indicates a much closer similarity with 

 the ovule described here. However, the megaspore membrane of S. 

 pettensis does not bear cell outlines or contain vesicles, and the 

 nucellar cuticle, which covers only its upper half, forms a long 

 protruding micropylar tube rather than a small beak. 



The presence oi Eiicommiidites pollen in both A. retemirum and 5. 

 pettensis is of importance, as the affinities ofEiicommiidites-bednng 

 seeds have been suggested to lie with the Gnetales, Bennettitales and 

 Pentoxylales (Hughes 1961; Pedersen et al 1989). It is not imposs- 

 ible that the obscured pollen grain bearing a median colpus within 

 the ovule described here could bear two subsidiary colpi which have 

 not been recognized. This would alter our view of the affinities of this 

 ovule considerably, and it is clear that more material is needed in 

 order to describe it more thoroughly. 



Order CONIFERALES 



INCERTAE SEDIS (family uncertain) 



Genus PSEUDOTORELLIA Florin 



1936a Pseiidotorellia Florin: 142. 



1957 Pseiidotorellia Florin; Lundblad: 760. [Florin"s diagnosis 



translated into English] 

 1969 Pseiidotorellia Florin; Watson: 248. [Diagnosis emended] 

 1 969 Tritaenia Magdefrau & Rudolf: 296. 



1990 Pseiidotorellia Florin; Bose & Manum: 49. (Diagnosis 

 emended] 



1991 Tritaenia Magdefrau & Rudolf: Bose & Manum: 14. 

 1 998 Pseiidotorellia Florin; Watson & Harrison: 240. 



2000 Tritaenia Magdefrau & Rudolf; Manum, Van Konijnenburg- 

 Van Cittert & Wilde: 257. 



Type species. Eeildenia iiordcnskjoeldii {NMhorsl). 1897: 56, pi. 

 3, figs 1 6-27 



Diagnosis, [slight emendation by Bose & Manum (1990) of the 

 translation by Lundblad (1957) of the original of Florin] Leaves 

 coriaceous, entire or microscopically dentate, almost linear to nar- 

 rowly tongue-shaped or obovate. straight or slightly falcate, with 

 their maximum width in the middle region or more apically; apex 

 obtuse; gradually narrowing towards base, hardly forming a petiole. 

 Veins moderate in number, dichotomizing chiefly in basal part, 

 ending separately at, or just below apical margin. Lamina with or 

 without resin ducts. 



