REVISION OF THE ENGLISH WEALDEN FLORA 



39 





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Fig. 6 A-E Phoenicopsis rincewindii sp. nov. All thinner (? lower) cuticle. A, widely distributed stomata scarcely avoiding veins. V.64526, LM. x 125; B, 

 holotype, outer surface less strongly ridged than that of thicker cuticle seen in Fig. 4, V.64527, SEM. x 500; C, stomata showing subsidiary cells with 

 more thickly cutinized periclinal walls than surrounding cells and pits overhung by papillae of lateral subsidiary cells; details of adjacent stomata on left 

 shown in Fig.SC, V.64526. LM. x 500; D, outside view of a stoma showing elongate pit overhung by subsidiary cellpapillae, V.64527, SEM. x 500; E, 

 cuticle viewed from the inside showing pitted anticlinal walls to ordinary epidermal cells and stoma, V.64527, SEM. x 500. 



Order GINKGOALES 

 Genus GINKGOITES Seward 



1919 Ginkgoites Seward: 10. [formal diagnosis not given] 



1935 Ginkgoites Seward; Harris: 48 



1936a G»7/:go/rei Seward; Florin: 105 



1968 Ginkgoites Seward; Tralau: 67 



1972 Ginkgoites Seward; Krassilov: 24 



1974 Ginkgoites Seward; Harris & Millington: 4. [dropped in 



favour of Ginkgo L.] 



1997 Ginkgoites Seward; Zhou: 190 



1999 Ginkgoites Seward; Watson et at 72 1 



Type species. Ginkgo obovata Nathorst 1886: 93, pi. 20. fig. 3. 

 [Cited by Andrews, 1970] 



Diagnosis, [emended by Watson et al 1999: 721] Fossil leaves 



occurring singly. Petiole distinct, enlarging abruptly at its top to form 

 lamina. Lamina with straight lateral margins, distal margin forming 

 arc of a circle; shallowly to deeply incised. Veins repeatedly 

 dichotomising, ending separately in distal margin. Cuticle where 

 known with haplocheilic stomata. 



Remarks. Fossil ginkgoalean leaf genera were discussed at length 

 by Watson etal(\ 999). both in their historical context and in the light 

 of recent discoveries (Kimurat'fo/ 1 983; Zhou & Zhang 1989, 1992; 

 Zhou 1991. 1997; Zhao et al 1993; Czier 1998) with two major 

 difficulties highlighted. First of all. the problem of dealing with 

 leaves which show wide variation in moiphology within a single 

 species is considerable. This is a difficult problem for whole leaf 

 specimens as well as fragmentary debris material. Secondly, the 

 argument against using the genus Ginkgo L. for fossil leaves in 

 which reproductive structures are completely unknown was 



