And Ginkgo Biloba Linn. Leaves
Comparative study between Ginkgoites tigrensis Archangel~ky and Ginkgo biloba Linn. leaves
Liliana Villar de Seoane
Liliana Villar de Seoane 1997. Comparative study between Ginkgoites tigrensis Archangelsky and GinA!go biIoba Linn. leaves. Palaeobotanist46(3) : 1-12. ' . A comparative study between leaves of Ginkgoites rigrrmsis Archangelsky'1965, which belong to the familf K.ark.e,ni:aceae and those of Ginkgo biloba L. included within the family Ginkgoaceae is realized, using lighI microscopy (LM) and scanning and transmission electron microscopy (SEM and TEM). The fossil cuticles occur in the sediments located in Baquero Formation (Lower Cretaceous), Santa Cruz Province, Argentina. The morphological, anatomical and ultrastructural analyses indicate great similarities between fossil and extant leaves. Key-words----Ginkgoalean leaves, Baquer6 Formation, Lower Cretaceous, Santa Cruz Province, Argentina.
Liliana Villar de Seoane, CONICEr, Divisi6n Paleobotanica, Museo Argentino de Ciencias Naturales "B. Rivadavia ". Av. A. Gallardo 470, (1405) Buenos Aires, Argentina.
RESUMEN
En el presente trabajose realiza el estudio comparado entre hojas de la especie f6sil Ginkgoites tigrrmsis Archangelsky 1965, pel1eneciente a la familia Karkeniaceae, y de la especie actual Ginkgo biloba L. pel1eneciente a la familia Ginkgoaceae, ambas familias incluidas dentro del orden Ginkgoales. Para efectuar el anAlisis cuticularse utiliz6 microscopia 6ptica (MO) y microscopia electronica de barrido y transmision (MEB y MEn. Los reslOS f6siles analizados fueron extraidos de sedimentitas organ6genas hlladas en la Formacion Baquer6 de la Provincia de Santa Cruz (Cret:!icico Inferior). Los resultados obtenidos con los anAlisis realizados, han demostrado la existencia de grandes semejanzas morfologicas, anat6micas y ultraestructurales entre las hojas de las especies Ginkgoites tigrrmsis y Ginkgo biloba.
mmr ~ ~ ~ ~ ~ 6,;;;;:un..Dn ..,..11&:0 .""lit-il,;;;...",-l v:ctfippj'r c6t d('1"lj(q(fi ~ ~ f ~ ~ ~ ~ ~ ~ ~ 311 ~ ~ ~ ~ ~ m-~ ~ ~~:rt~I ~ ~ ~ ~ it 'h1 cf; 311CflIR described by Archangelsky (965) with light micros MATERIAL AND MElHODS copy (LM). The fossil materials occur in the Baquer6 In Argentina, ginkgophyte leaves have been Formation, Estancia Bajo Tigre. This Formation is recorded from the Lower Permian of Chubut located to the south of the Deseado River, be Province (Cuneo, 1987). The genus Ginkgottes tween the parallels 47°-49° and the meridians 68°• occurs in the Triassic of Neuquen and Mendoza 69° 30', Santa Cruz Province, Argentina (Text Province (Frenguelli, 1946), the Lower Jurassic of figure 1). In the Estancia Bajo Tigre the fossil Chubut Province (Feruglio, 1933), the Upper plants occur in lenticular beds of brownish colour. Jurassic and Lower Cretaceous of the Lago San Paleobotanical and palynological studies Martm, Santa Cruz Province and Graham Land, (Archangelsky & Gamerro, 1966a, 1966b) for the Antarctica (Halle, 1913), and in the Tertiary strata of Baquero Formation suggested a Lower Cretaceous Chubut Province (Archangelsky, 1965) and Rio Negro Province (Berry, 1938). The studied cuticles age, 120 million years (Archangelsky, 1967). Fos were found in the Baquer6 Formation, Santa Cruz sils are mainly represented by well preserved Province, associated with seed-bearing structures leaves. Cuticles were prepared for both light and belonging to the species Karkenia incurva electron microscopy. The material was easily sepa Archangelsky 1965. rated from the matrix and cleaned with dilute sodium hypochlorite. Among living plants there is no more striking I ~~ '" \4' example of a species which recalls the past than 1'~ W- .. __ ... Ginkgo biloba that occurs naturally in Chekiang SANTA Province, China; only known in cultivation inJapan, W Korea and Manchuria where it is used principally -..J around temples. Used as a street tree in Japan and Ir.:l:. . . _. _ _ .:_ '4'(' U . introduced into Europe from Japan in 1727 (Gifford Ea. BAJO TIGRE & Foster, 1989). For the first time, Kaempfer (712) described this ~...... tree and gave the generic name Ginkgo. In 1690, he travelled to Orient, where he saw "an uncommon tree in Europe, with adiantiform leaves". In 1771, Linnaeus adopted the genus given by Kaempfer and established the species G. btloba. In 1900, Seward and Gowan realized a complete description of the "Maidenhair tree". More recently, the species Ginkgo biloba was studied by Chamberlain (935), Spome (965), Napp-Zinn (966), Gifford and Foster (989) ~K-: and Page (990) with general descriptions. KrUssmann 11, (985) analyzed its anatomy in relation With the Ten-flgw:e I-Map shoWing the location of the Estanicia Bajo Tigre environment. (Baquer6 Fonnation). PlATE 1 1-6. Ginkgoites tigrensis Archangelsky 1. Gene'ral view of the leaves. BA Pb 11557. Scale bar • 1 em. 4. Details of cells in the internal adaxial epidermis. BA Pb MEB SO. 2. Internal abaxial epidermis. BA Pb MEB SO.Scale bar • 100 11m. Scale bar· SO11m. 3. Stomata (arrows) on the external abaxial epidermis. BA Pb MEB SO. 5. Details of a stoma. BA Pb MEB SO.Scale bar· 10 11m. Scale bar • SO11m. 6. Details of guard cells. BA Pb MEB SO.Scale bar· 10 11m 4 TIlE PALAEOBOTANIST The recent material was collected at the Buenos 11585,11586,11587 and 11588; BA Pb Pm 237, 238, Aires Botanical Garden. Fossil and extant leaves were 239,240 and 253; BA Pb MEB50; BA Pb MET 153. mounted in glycerine-jelly for observation with light Locality-Meseta Baquero, Estancia Bajo Tigre. microscopy, or directly on cylindrical stubs and coated with gold-palladium for scanning electron microscopy Stratigraphic hOrizon-Baquer6 Formation, (SEM). Observations were made with a lEOL T-lOO Lower Cretaceous. SEM at the La Plata Natural History Museum. Emended diagnosis-Ultrastructurally, the ex For transmission electron microscopy (TEM) ternal wall of the epidermis is composed by a cuticle fragments were embedded in Spurr low cuticular membrane and a cellular wall. A thin viscosity resin (Spurr, 1969). Sections were cut with cuticle proper, a compact upper layer and a reticu a diamond knife and mounted in single hole grids late lower layer formed the cuticular membrane. coated with Formvar. Observations were made on a Cellular wall with a lower electronic density. Zeiss EM 109 of the Electronic Microscopy Service at the Cellular Biology Department, Medicine Faculty, Description-The leaves are simple and ~mallto Buenos Aires University. medium. They are flabelliform, up to 4.5 cm long The fossil type specimens are deposited at the and 5 cm wide. The laminae are divided in three to Paleobotanical Collection of the Buenos Aires Natu six segments. The segments are loriform, up to 4 cm ral History Museum (BA Pb) and the recent speci long and 0.7 cm wide, united by only one decurrent mens at the Plant Biology Department, Natural base. They have rounded apex and straight margins Sciences Faculty, Buenos Aires University. Hickey's (PI. 1, fig. 1). The petioles are slender, up to 3 cm classification (1974) was used for the morphological long and 0.1 cm wide. The veins radiate from the descriptions, whilst terminology ofHolloway (1982a, base, dichotomously forked, with a concentration of 1982b) and Lyshede 0978, 1982) was used for the about 18-20 veins per centimetre, up to 14 present ultrastructural analysis. in each segment. Two veinsseem to be present in the petioles. SYSTEMATIC DESCRIPTION The leaf surfaces are covered with epicuticular Family-Karkeniaceae waxes. Adaxial epidermis has rectangular to Genus--GinkgoUes Seward 1919 isodiametric cells, 31-70 pm long and 18-26 pm wide. Type species-Ginkgottes obovata (Nathorst) They often occur in rows, have microgranular sur Seward 1919 face, their walls are thickened and have irregular Ginkgottes tigrensts Archangelsky 1965 margins with sinuosities up to 2.5 pm wide (PI. 1, fig. PI. 1, figs 1-6; PI. 2, figs 1-4 4). Stomata absent on the petiole and the base of the Ginkgottes ttgrensis Archangelsky, Bull. Brit. lamina, but present on segments between veins. Mus. (Nat. Hts!.) Geol., 10 (5), pp. 125-128, pI. 3, fig. They are irregularly disposed. 22 and pI. 4, figs 23-26 (965). Abaxial epidermis has rectangular to isodiamet Specimens studied-BA Pb 11556, 11557, 11558, ric cells, 39-78 pm long and 18-34 pm wide. The cells 11559, 11560, 11561, 11581, 11582, 11583, 11584,' have the same characters and disposition in the PlATE 2 c - cuticle proper; Ul. - upper layer; LL - lower layer; CW - cellular wall. 1-4. Ginkgoites tigrensis Archangelsky 1. 1'5 section of the external wall of the epidennis with SlOma (arrow). 3. 1'5 section of a periclinal wall. BA Pb MET 153. Scale bar - 111m. BA Pb MET 153. Scale bar - 10 11m. 4. 1'5 section of the extemal wall of the epidennis. Detail. BA Pb MET 2. 1'5 section of a stoma. BA Pb MET 153. Scale bar - 111m. 153. Scale bar - 111m. • V) ~. ~« .....l ~ ~ l:l:l 0 ~ .. t3 • Cl ~ ~ f ~ ~ r::: \P ~ »' ~ t3 6 THE PALAEOBOTANIST adaxial epidermis, but the walls are more thin (PI. 1, region has not been found in the cuticles described fig. 2). in the present paper. Stomata are irregularly disposed (PI. 1, fig. 3). Ginkgoites digttata (Brgn.) from the Lower Ju Stomatal apparatus up to 62 pm in diameter and are rassic of Chubut Province, differs in having entire circular or oval on both cuticles. They are actinocytic leaves, bilobed or divided in several segments or tetracytic with 6 or 4 subsidiary cells, respectively. (Feruglio, 1933); Ginkgottes patagonica Berry 1938 The subsidiary cells have striate walls that form a ring from the Lower Tertiary of Neuquen Province, has of.2-3 pm high surrounding the guard cells (PI. 1, fig. leavesdeeply divided in several segments; Ginkgoites 5). Guard cells slightly sunken in a pit and cutinized crassipes Feistmantel from the Lower Permian of (PI. 1, fig. 6). Chubut Province, differs in having entire leaves; Ultrastructurally, the external wall of the epider Ginkgotteseximia Feruglio 1942 from Piedra Shotel, mis is composed by a cuticular membrane and a Chubut Province (Lower Jurassic), has entire and cellular wall (PI. 2, fig. 1). The cuticle proper is 0.25 bilobed leaves with long petioles; Ginkgottestaeniata pm thick (PI. 2, fig. 4), the upper layer is 1.0 pm thick, (Geinitz) Frenguelli 1946 from the Triassic of Neuquen Province, has small leaves divided in few segments, compact and homogeneous and the lower layer is small stomata only present in the abaxial cuticle and 1.5 pm thick, slightly reticulate with thin channels few stomata and papillae in the adaxial cuticle; and irregularly distributed (PI. 2, figs 2-4). The channels Ginkgoites trnncata Frenguelli 1946 from Potrerillos are anastomosed. Near the cellular wall they are Basin, Mendoza Province (Upper Triassic), differs in parallel to the surface, but near the upper layer they having entire and triangular leaves with truncate may arch up to 90° and are perpendicular to the apex. surface. Both layers have small and irregular holes (PI. 2, figs 3,4). The rest of the cellular wall is 1.5 pm FaoiUy~Uikgoaceae thick and has a lower electroniC density (PI. 2, fig. 4). GenlJ5---Glnkgo Linnaeus 1771 The anticlinal walls have an important development Type species-Ginkgo hi/oha Linnaeus 1771 ofthe upper layer. The periclinal walls ofthe stomata Ginkgo hi/oha Linn. have the lower layer very developed. PI. 3, figs 1-6; PI. 4, figs 1-4 Compartsons-GinkgottesticoenstsArchangelsky Descrtption-The leaves are simple and small to 1965, the other species described in the Baquer6 medium. Laminae flabelliform, up to 8 cm wide, Formation, differs from Ginkgottes tigrenstsin shape, entire, but more frequently bilobed, or subdivided size and anatomical structures. Ginkgoites ticoensis into several wedge-shaped lobes. Leaves with has smaller leaves divided in 4 segments, smaller rounded apex slightly serrate, straight margins and segments with 12 veins per centimetre, polygonal decurrent base (PI. 3, fig. 1). The petioles are slender, epidermal cells with a strong hollow papilla that not up to 3 cm long and 0.1 cm wide. The veins are form rows and smaller stomata only present in the radially disposed from the base. They are sub abaxial cuticle. Ultrastructurally, Taylor, W. et al. parallel, dichotomously forked, with a concentra (989) studied cuticle fragments of Ginkgoites tion of about 18-20 veins per centimetre. Two veins tigrensts finding "approaching the outer cuticle are present in the petioles. The foliage leaves occur surface, a well developed poly-Iamellate region of on long shoots or crowded at the apex of short 25-44 nm in overall extent". That poly-Iamellate shoots. PlATE 3 1-6.Ginkga hilaba L. 1. Leaf. BA 74784. Scale bar - 0.5 em. 4. Details of the stomata (arrows). BA Pb MEB 51. Scale bar - 50 11m. 2. Details of adaxial epidennal cells. BA Pb MEB 51. Scale bar - 50 IJ.fTl 5. Details of the guard cells. BA Pb MEB 51. Scale bar - 10 11m. 3. Stomata (arrows) on the abaxial epidermis. BA Pb MEB 51. Scale 6. Details of the subsidiary cells. BA Pb MEB 51. Scale bar - 100 11m. bar - 10 11m. 8 THE PALAEOBOTANIST Surface coveredwith abundant epicuticular waxes leaves which are referred to three genera: Trtchopttys of thin and short fibrous aspect (PI. 3, figs 5, 6). Saporta, Phylladoderma Zalessky and Sphenobaiera Adaxial and abaxial epidermis are formed by rectan Florin. gular to polygonal cells irregularly disposed (PI. 3, During the Mesozoic, the Ginkgoales have their figs 2, 3). Their walls are slightly thickened and greatest prominence, especially in the Jurassic-and sinuous. Each abaxial epidermal cell forms one or Lower Cretaceous, their polymorphic leaves were two papillae of 17 ~m in diameter and 15-28 ~m grouped in two families, the Ginkgoaceae and the height (PI. 3, fig. 4). Phoenicopsiaceae. The family Ginkgoaceae was Stomata on the abaxial epidermis, irregularly represented by Ginkgo L., Ginkgoidium Yokoyama, disposed between veins. Actinocytic stomatal appa Ginkgottes Seward and Baiera F. Braun; whilst the ratus, up to 90 ~min diameter', with 6 to 7 subsidiary family Phoenicopsiaceae was represented by cells (PI. 3, figs 5, 6). Each subsidiary cell forms a Phoenicopsts Heer, Culgowerta Florin,Windwardia papilla oriented to the pit. Guard cells sunken, with Florin, Eretmophyllum Thomas, Stephenophyllum cuticular ridge surrounding the mouth (PI. 3, figs 5, 6). Florin, Pseudotorellia Florin, Arctobaiera Florin, Ultrastructurally, the external wall of the epider Hartzia Harris, Czekanowskia Heer, Sphenobaiera mis is formed by a cuticular membrane and a cellular Florin and Glossophyllum Krausel During the Upper wall. A thin cuticle proper, a compact upper layer Cretaceous, the order Ginkgoales begins to disap and a reticulate lower layer formed the cuticular pear and in the Lower Cenozoic the group was only membrane (PI. 4, figs 1, 2). The cuticle proper is 0.25 represented by the family Torelliaceae with the ~m thick; the upper layer, up to 0.75 ~m thick, is genera Torellia Heer (Tralau, 1968). compact and homogeneous (PI. 4, fig. 4). The lower The oldest fossils belonging to the genus Ginkgo layer, up to 1.0 ~m thick, is reticulate, with pecti were found in the Lower Jurassic of Fergana in the naceous microchannels that are perpendicular to the southern Asiatic part of the Soviet Union, and were surface. The cellular wall is lamellate, up to 2.0 ~m described as G. digttata (Brik, 1953; Vasiljevskaja, thick, with superposed lamellae separated by trans 1956). During the Lower Cretaceous, the polymorphy lucent channels that anastomose, and are parallel to in foliar remains indicates the rise of new species. At the surface (PI. 4, fig. 4). The anticlinal walls have an the Middle Tertiary, the genus retained its circum important development ofthe upper layer (PI. 4, fig. polar distribution, being known throughout Eurasia 3). The subsidiary and guard cplls have a thick and Northern America. At the Upper Miocene, cuticle and their cellular wall is very lignified, Ginkgo becomes to be extinct in North America and especially the external periclinal wall. during the Pliocene the genus seems to be confined to Eurasia, taking place in China between the Upper DISCUSSION Pliocene and the modern times. The order Ginkgoales appears in the Upper At the beginning of the Mesozoic, there exist Paleozoic. The oldest fossil materials from the Lower several lineages of Ginkgoales, characterized by Permian were represented by different types of different leaves and seed-bearingstructures. Accord- PlATE 4 E• epidermis; M• mesophyll; C• cuticle proper; Ul. • upper layer; LL • lower layer; CW • cellular wall. 1-4. Ginkgo. biloba L 1. TS section of the abaxial epidermis. BA Pb MET 161. Scale bar· 10 3. TS section of an anticlinal wall (arrows). Detail. BA Pb MET 161. pm. Scale bar - 1 pm. 2. TS section of the abaxial epidermis. Detail. BA Pb MET 161. Scale 4. TS section of the external wall of the epidermis. Detail. BA Pb MET bar· 1 pm. 161. Scale bar· 1 pm. - Ci ~ ~ ~ ~ 0- ~ 0 ItJ.l ~ 0 w ing to the inflorescence associated, the leaves were Stanislavsky 0971, 1973) described Toretzta re-grouped in four different families, such as angusttfolta from the Upper Triassic of Novoraick Trichopityaceae, Umaltolepidaceae, Karkeniaceae Formation (Ukraine). The vegetative shoots bear and Ginkgoaceae (Zhou Zhiyan,199l). buds covered with scales spirally arranged. 2 to 3 ovule-bearing organs are given off from the axils of The Trichopityaceae was the oldest family and bracts on the short shoots. The ovules are inverted. disappeared at the end of the Paleozoic; the The genera Umaltolepts and Toretzta belong to the Umaltolepidaceae and Karkeniaceae were Mesozoic family Umaltolepidaceae and Karkenta to the family families that disappeared in the Upper Cretaceous; Karkeniaceae. and the Ginkgoaceae is the modem family with the only one living species Gtnkgo btloba. Zhou and Zhang (988) described Ytmata recurva from the Middle Jurassic Yima Formation, Henan, The family Trichopityaceae was represented by Central China. The fertile shoots were composed of Trtchopitys heteromorpha Saporta 1875 and Florin a peduncle and up to 9 terminal ovules which were (949) described the species T. heteromorpha from large, sessile, contiguous, orthotropous but mostly the Lower Permian of Lodeve (France), as vegetative recurved. Ytmata was associated to primary short shoots with leaves spirally arranged and divided in shoots with Batera-type leaves. These ·leaves were 4 to 8 segments. In their middle region the long deeply divided into numerous narrow lobes, form shoots carry furcated ovulate shoots with 3 to 20 ing as a whole one third to one fourth of a circle. terminal, inverted and orthotropous ovules. Also, Zhou and Zhang 0988, 1989) described Krassilov 0970,1972) studied the tafoflora from the species Gtnkgo ytmaensts from the Middle the Bureja River Basin of Siberia (Upper Jurassic Jurassic Yima Formation of Henan, Central China. It Lower Cretaceous). Within the order Ginkgoales, he differs from G. btloba L., in having more deeply described two different types of female inflores divided laminae and normally more (2-4) seeds cences (Karkenta and Umaltolepts) and several which were attached terminally to pedicels rather types of leaves. Umaltolepts vachrameevtt from the than directly to the peduncle as in the case of the Talunjan Formation ofthis area (UpperJurassic) was extant species. The extant species has female flowers described as the Type species, but there is another long stalked, solitary, axillary, with 2 opposing ovules at the end of the thickened stalk apex. The species of Umaltolepts, U. rartnervts from the Ulgar Formation of the same area (Lower genera Ytmata and Gtnkgo belong to the family Ginkgoaceae. Cretaceous). This type of female reproductive organ consists of a stalk and a terminal bract. This bract is GENERAl. CONCLUSIONS elongated, entire or divided into two lobes that abaxially had a single seed. These structures were The family Karkeniaceae was proposed by associated to leaves of the Pseudotorellta-type, with Krassilov 1970 and includes a single genus with two laminae undivided, roundish apex and stomata on species from the Upper Jurassic and Lower Creta abaxial epidermis only. The other species Karkenta ceous strata of Siberia and Argentina. Karkenta astattca is composed of a central axis with erect or tncurva Archangelsky 1965 is the only ginkgoalean incurved ovules, densely packed and associated to fossil known outside Laurasia. Karkenta was associ leaves of EretmophyllumThomas and Sphenobatera ated with sessile leaves during the Upper Jurassic type. Eretmophyllum has undivided leaves with and petiolate leaves during the Lower Cretaceous. roundish apex, stomata on abaxial epidermis only In the Baquero Formation, the family and rounded papillae whilst, Sphenobatera has Karkeniaceae is represented by the leaves of small leaves deeply lobed. Gtnkgottes ttgrensts and the associated ovule-bear- SEOANE-COMPARATIVE STUDY BETWEEN GINKGOITES T7GRENSIS AND GINKGO BILOBA LEAVES 11 ing organ Karkenta tncuroa. This structure' is com Archangelsky S 1967. Estudio de la Formaci6n Baquer6, Creto1cico Inferior posed of a central axis and up to 100 small, incurved de Santa Cruz, Argentina. Rev. Mus. La Plata (N.S.) Pa!. S: 63-171. Archangelsky S & Gamerro ]C 1966a. Estudio palinol6gico de la and orthotropous ovules, densely packed. On the Formaci6n Baquer6 (Creucico), provincia de Santa Cruz. II. basis of the close relationship between the Amegbiniana 4(6): 201-209. Karkeniaceae and Ginkgoaceae, the genus Gtnkgottes Archangelsky S & Gamerro ]C 1966b. Estudio palinol6gico de la Formaci6n Baquer6 (Creto1cico), provincia de Santa Cruz. III. was compared with the extant genus Gtnkgo. Amegbiniana 4(7): 229-236. Morphologically, the leaves of fossil and extant Berry EW 1938. Tertiary flora from the Rio PichileufU. Argentina. SpeCial genera are different. The fossil leaves are smaller and Paper Geol. SOC.Americana 12: 1-140. Brik M] 1953. The Mesozoicflora of tbe Vostoljno-Pergana coal basin. divided in several segments whilst, the extant leaves Cuneo R1987. Sobre la presencia de probables Ginkgoales enel Permico are longer and entire, but more frequently bilobed Inferior de Chubut. Argentina. AClas VII Simposio Argentino Paleo or subdivided into several wedge-shaped lobes. hot. Palinol. : 47-49. Buenos Aires. Chamberlain] 1935. Gymnosperms structureand eoolution. The Univer The anatomical analysis between Gtnkgottesand sity of Chicago Press, Chicago. Gtnkgo has indicated several affinities. The two Feruglio E 1933. Fossili Liassici della Valle del Rio Genua (Patagonia). In: genera have fan-shaped leaves with veins radially Giorn. di Geologia (Ann. R. Mus. Gool. Bologna) 9: 1-64. Imola. disposed from the base, epicuticular waxes and Feruglio E 1942. La Flora Lio1sicadel Valle del Rio Genoa. Ginkgoales et Gymnospermae incertae sedis. Notas delMuseodeLaPlata. PaJeontol. rectangular to polygonal epidermal cells with sinu 7(40): 93-110. ous and thick walls. The fossil genus has a smooth Florin R 1936. I. Die fossilen Ginkgophyten von Franz-]oseph-Land nebst epidermal surface and actinocytic or tetracytic sto Erorterungen tiber vermeintliche Cordaitales mesozoischen Alters, matal apparatus with a ring surrounding the guard and III. Allgemeiner Teil. Palaeontographica 881-82. Florin R 1949. The morphology of Tricbopitys heteromorpba Saporta, a cells whilst, the extant genus has a papillose epider seed plant of Palaeozoicage, andthe evolution ofthe female flowers mal surface and actinocytic stomatal apparatus with in the Ginkgoinae. Acta Horti Bergiani 1S(5): 79-109. papillae oriented to the pit. Frenguelli] 1946. La Flora del Gondwana Superior en la Argentina. NOlas del Museo de La Plata. Paleonto!. 11(87): 101-127. Ultrastructurally, the comparison of the external Gifford EM & Foster AS 1989. Morphology and eoolurion of vascular wall ofthe epidermis between Gtnkgottesand Gtnkgo plants. Freeman WH (Editor). New York. has demonstrated that both the genera have a thin Halle TG 1913. Some Mesozoic plant-bearing deposits in Patagonia and cuticle proper, a compact and homogeneous upper Tierra del Fuego and their floras. K. suensk. VetenskAkad. Hand!. S1(3): 1-58. layer and a reticulate lower layer. However, Gtnkgottes Harris TM 1935. The fossil flora of Scoresby Sound. East Greenland, 4. has thicker upper and lower layers than Gtnkgo. The Ginkgoales, Coniferales, Lycopodiales and isolated fructifications. existence of morphological, anatomical and ultra Medd. Granland 112, 1. structural similarities in both of the fossil and living Hickey L 1974. Clasificaci6n de la arquitecrura de las hojas de Dicotiled6neas. Bol. de la Soc. Arg. de Bot. 16(1-2): 1-150. genera corroborates a close relationship between Holloway P] 1982a. Structure and histochemistry of plant cuticular the Karkeniaceae and Ginkgoaceae leaves. membranes: an overview. In : Cutler DF, Alvin KL & Price CE (Editors}- The plant cuticle: 1-31. London. ACKNOWLEDGEMENTS Holloway P] 1982b. 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