FOSSIL POLLEN OF TILIA FROM THE EAST ANGLIAN FENLAND

Abstract

SUMMARYAnalysis of a large number of fossil pollen grains of Tilia from the East Anglian Fenland, led to examination of the characters that might be employed to separate T. platyphyllos from T. cordata. Certain characters were discarded hut mesh structure and size in surface reticulation, characters since accepted by other authors, were regarded as satisfactory and made the basis for classifying fossil grains. The results indicated native British status for both species of lime from pollen-zone Vila onwards, with T. cordata much the commoner, and very high relative frequencies of Tilia pollen in zone Vila and diminution zone by zone thereafter to levels below 0.5% of total tree pollen.Whilst working in the Cambridge Botany School during the period 1956-59 upon the vegetational history of sites on the western border of the East Anglian Fenland, large numbers of fossil pollen grains of Tilia were encountered and the attempt was made to refer them to the two species that have been considered native to Britain, T. cordata Mill., and T. platyphyllos Scop. An attempt was made to use various criteria accepted at that time, but finally dependence was placed on the character, visible under the oil-immersion objective, that in the exine reticulation pattern of T. platyphyllos most of the meshes contain a central spot of the same refractive index as the reticulum itself, whereas in T. cordata the meshes of the reticulum are empty. This feature was independently recognized by Erdtman (1956), andPraglowski (1962). This feature has been subsequently elucidated by electron-microscopic investigations (Chambers and Godwin, 1961, 1971) and is a substantial part ofthe basis on which Beug (1971) and Andrew (1971) rely for separating pollen of the two species.The samples of fen peat were prepared in the usual way by heating in 10% NaOH, followed (after sieving) by ehlorination, acetolysis and mounting in glycerine jelly stained with safranin.With the exine pattern as criterion the fossil pollen was referred to T. cordata and T. platyphyllos. A few intermediates were disregarded for this purpose. Fifty grains of each were photographed, at a magnification of x 375 and all the negatives were enlarged to give prints at a uniform magnification of x 1125. Between two and six photographs were made of each grain at appropriate depths of focus. The following dimensions were then collected from the photoprints.(i) Mean diameter: from the polar view of each grain, the mean of three diameters was taken, each extending from a pore to the opposite face (Fig. ia).(ii) Pore breadth/depth ratio: as measured from side view of the pore with the grain in polar aspect (Fig. ib). 693

Biological Flora of the British Isles:Tilia platyphyllos

“…years BP, before the submergence of the southern North Sea and Channel, when, without circulation of Atlantic currents, the climate was more continental. A record based on pollen size is from a Mesolithic site at Addington in Kent (Burchell & Erdtman, 1950; Erdtman, 1943) and several records are from the margins of the East Anglian Fens (Mittre, 1971). Recent investigations of a site near Lewes in Sussex (Waller & Early, 2015; Waller & Hamilton, 2000) are particularly relevant to the present distribution of probably native localities in the Wealden area.…”

World Pollen and Spore Flora 23. Malvaceae Adams. P.p. Subfamilies: Grewioideae, Tilioideae, Brownlowioideae

“…Thanks are also due to M. De Castellis et al 1985Dnyansagar & Gaoli 1965Fisher 1890Guggenheim 1975Hesse 1978Jain & Nanda 1966Kasartseva 1982Mai 1961Mittre 1970Moore & Webb 1978Patel & Datta 1958Qaiser & Perveen 1997Rao & Rao 1952Sharma 1969Srivastava 1976Stockmarr 1973Tang & Gao 1993Tarnavschi & Serbanescu-Jitariu 1968Tirel et al 1996Wang 1960Zhang & Chen 1984Zhuge 1990 …”

The Pollination Biology of Tilia

“…However, the intrafloral behavior of the members of such genera as Andrena, A pis, Bombus, Dialictus, Eristalis, Peridroma and Pseudaletia was such as to effect pollination in the "mess and soil" sense of Faegri and van del' Pijl (1971). No attempt was made to ascertain which species of TWa pollen were carried because recognition of the pollen is difficult (Andrew, 1971;Chambers and Godwin, 1971;Mittre, 1971). Of the groups considered important in Tilia pollination, moths show the lowest frequency (0.3) of non-Tilia pollen.…”

“…Hickok and Anway (1972) find that, on the basis of morphological and chemical char-acters, there is a latitudinal continuum between the three taxa and they conclude that Jones' three species should be treated as one. For the Old World species there are a number of references to hybridization, from studies of both contemporary (Pigott, 1969, and see reference in Jones, 1968) and fossil (pollen cores: Andrew, 1971;Mittre, 1971) material. The lack of clear differences in floral morphology described for the species studied here probably means a lack of recognition by pollinators.…”