Pollen morphology of the genus Paliurus (Rhamnaceae)

Transcription

1 Grana ISSN: (Print) (Online) Journal homepage: Pollen morphology of the genus Paliurus (Rhamnaceae) Carsten Schirarend To cite this article: Carsten Schirarend (1996) Pollen morphology of the genus Paliurus (Rhamnaceae), Grana, 35:6, , DOI: / To link to this article: Published online: 01 Sep Submit your article to this journal Article views: 303 Citing articles: 7 View citing articles Full Terms & Conditions of access and use can be found at

2 Grana: 35: , 1996 Pollen morphology of the genus Paliurus (Rhamnaceae) CARSTEN SCHIRAREND Schirarend, C Pollen morphology of the genus Paliiiriis (Rhamnaceae). - Grana 35: ISSN The pollen morphology of the genus Paliirrus and the 5 species it comprises is described. Consistent with the general morphological pattern of the family Rhamnaceae, the pollen grains of Puliuriis are uniformly isopolar, radially symmetrical. 3-(zono)-colporate and angulaperturate. Despite this general infrageneric uniformity, certain differences and trends can be recognized with respect to pollen size, shape, and tectum architecture. C. Schirareii, Uniwrsiliit Hamburg, Irisririrr fur AlIgeiiieiiie Botaiiik urid Botanisclicr Garreit, Ohnhorst- Sir Hainburg, Germail): (hlariiucript accepted 15 February 1997) In preparation for a taxonomic revision of the genus Pnlizinrs (Schirarend & Olabi 1994) comparative palynological studies were carried out using LM, SEM and TEM. Morphologically the genus is well distinguished by its unique circular winged fruits, the presence of 1-2 straight or recurved stipulary spines and the triplinerved, often + asymmetric leaves. The distribution of the genus is split into a western European- West Asiy-North African part and an East Asian part, separated from each other by about 4500 km of continental Asia. The western sub-area, which is exclusively inhabited by P. spiiza-cliristi, extends over most of the coastal regions of the Northern and Eastern Mediterranean, parts of Northern Africa and eastward to Western Asia. The eastern sub-area comprises parts of China, Korea, Japan, Taiwan and Vietnam. Previous palynological studies of the genus are rather limited and restricted mainly to regional or local pollen floras (Horowitz & Baum 1967, Huang 1972, Papagiannes 1974, Schirarend & Kohler 1993). MATERIALS AND METHODS Polliniferous material from herbarium specimens was obtained from the following collections: A, B, BHU, BHU-PM, E, GB, GH, HAC, HAJB, HAL, HBG, JE, L, M, P, PRC, S, UPS, US, W. For light microscopy (LM) pollen samples were acetolysed and mounted in glycerine-jelly. A ZEISS Amplival microscope equiped with an planachromate objective (x 100, NA 1,25) and compensating eyepieces x 10 was used. Generally ten measurements of pollen size (polar and equatorial diameter), apocolpium and aperture diameter, and exine thickness were made for each specimen (Table I, 11). The Photomicrographs were taken at a magnification of x For scanning electron microscopy (SEhl) pollen samples were acetolysed and transferred to specimen stubs. After coating with gold-palladium they were studied with JEOL JSM-25, IS1 Super- IIIA and Phillips 515 microscopes. For transmission electron microscopy (TEM) the polliniferous material was treated for about 50 hours with TAG solution, consisting of 1% tannic acid and I% glutaraldehyde in 0,l M phosphate buffer at ph 7,4. After dehydration in an acetone series the pollen Erains were embedded in Epon araldite and sectioned with a diamond knife on an LKB Ultra-microtome. Observations and photomicrographs were taken on a ZEISS 10 transmission electron microscope. 0 I996 Scandinavian University Press. ISSN TERMINOLOGY The terminology follows, Faegri & Iversen (l989), Hideux & Ferguson (1976), Nilsson & Muller (1978), Nilsson & Praglowski (1992), Praglowski & Raj (1979), Punt et al. (1994), and Schirarend 8: Kohler (1993). The quantitative values given in the descriptions and tables represent the means or ranges of the means and in parentheses the absolute range of the measurements. GENERAL POLLEN DESCRIPTION Light microscopy (Figs. 1-4, 12-15,23-26,34-37,4649) Pollen. radially symmetrical, isopolar, 3-(zone)-colporate, angulaperturate, suboblate, oblate-spheroidal to prolatespheroidal, polar axis (P) (16-28) pm, equatorial diameter (E) (18-29) pm, form index (FI, expressed as mean P/E ratio) ( ). Polar view (amb) triangular to sub-triangular, mesocolpium plane straight to +convex, apocolpium comparatively small, diameter 3-6(-8) pm. Equatorial view elliptic to subrhomboidal, with - +protruding equatorial caps. Colpi always very long, extending over about 4/5 of the length of the polar axis. Endoapertures (ora) &narrowly lalongate, elliptic to almost circular, diameter 1-5 x 2-7 pm, surrounded byf distinct, laterally opened nexine thickenings. Exine 1-2 pm thick, with conspicuous thinning parallel to the colpi, stratification nondiscernible in light microscope, LO-pattern -t densely punctate or rugulate. Electron microscopy SEA1 (Figs. 5-11,16-22,27-33,40-45,50-56) Colpi comparatively narrow and shallow, equatorially fwidened, colpus ends +rounded to pointed, colpus margin Adistinct, mainly low, and rather poorly developed, narrow, often restricted to the innermost rim of the colpus, nonsculptured, with loosely scattered perforations, colpus membrane &coarsely granular, rarely almost psilate. Grana 35 (1996)

3 348 C. Scliirareiid Table I. Qiiarititative pollen characters of Paliiirirs hemleyariiis, P. hirsutris, P. orientalis and P. rariiosissiiiiirs. Species & specimens Polar axis (P) Equatorial diameter (E) Form index Endoaperture (w) (P/E) diameter (p) P. liernsleyarius Farges s.n. (P) Henry 6379 (GH) Jiang & Tao 72 (A) Rock 3005 (A) Tsiang 9746 (W) 20 (19-23) 23 (24-25) 20(18 23) 19 (17-20) 23 (20-25) 23 (22-24) 24 (23 25) 23 (21-24) 21 (19-22) 24 (22 28) 0.87 ( ) 0.96 ( ) 0.89 ( ) 0.90 ( ) 0.95 ( ) 2x x 1 2x x x2-6 P. Iiirsutirs Balansa 3978 (P) Ching 2744 (A) Chung 42 (A) P. orientalis Delavay 239 (P) Forrest (E) Henry 9327 p (A) Schneider 1433 (A) Ten 214 (E) P. ru~~iosissiiiriis Chung 2797 (A) Chung 6356 (A) hlatsumura s.n. (UPS) Oldham s.n. (W) 19 (I8 20) 18 (17-21) 19 (18-21) 21 (19-22) 20 (19-22) 18 (17-19) 18 (16-20) 20(18 21) 18 (16-20) 19 (17-22) 19 (17-21) 20 (18-22) 22 (21-23) 22 (19-24) 22 (21-24) 22 (21-23) 22 (21-24) 20 (19-22) 20(18 24) 20 (19-22) 23 (21-24) 22 (20-25) 22 (21-24) 23 (21-24) 0.86 ( ) 0.82 ( ) 0.86 ( ) 0.95 ( ) 0.93 ( ) 0.90 ( ) 0.88 ( ) 1.02 ( ) ( ) 0.86 ( ) 0.86 ( ) 0.83 ( ) 2-3 x x x 3-5 2x34 2x x x 5-6 2x3 34x4 6 2x3-4 2x x 4-6 Table 11. Qiiarititatire polleri characters of Paliiirirs spiria-eliristi. Polar axis (P) Equatorial diameter (E) Form index Endoaperture Specimens (iim) (w) ( P/E 1 diameter (pm) Adamovic 1320 (W) 25 (23-26) 24(23 25) 1.04 ( ) 2x34 Ascherson s.n. (W) 23 (20 27) 24 (22-26) 0.96 ( ) 2x4 5 Bierbach s.n. (W) 21 (20 25) 22 (20-25) 0.95 ( ) 1-2 x 3-6 Bommuller s.n. (A) 24 (22-26) 24 (23-28) 1.00 ( ) 2-5 x 3-6 Bourgeau 499 (W) 23 (25-27) 25 (23-28) 0.92 ( ) 3x1 Keller s.n. (W) 23 (21-95) 24 (23-25) 0.96 ( ) 2x4 5 Krendl s.n. (W) 25 (23-26) 24 (23-25) 1.04 ( ) 2x34 hlattfeld 2636 (A) 30 (28-32) 27 (24-29) 1.12 ( ) 2-3 x 1 Nyaradi & Borza 571 (W) 25 (23-28) 26 (24-29) 0.96 ( ) 2-3 x 3-5 Quasdorf 4992 (B) 23 (21-24) 23 ( OO ( ) 2x3 5 Ronniger s.n. (W) 23 (22-26) 22 (19-24) 1.04 ( ) 2x24 Vent s.n. (B) 25 (21-26) 25 (22 29) 1.00 ( ) 2-3 x 1 Witting s.n. (W) 21 (17 23) 22 (21-25) 0.95 ( ) 1-2 x 3-6 Exine sculpture rugulate to fossulate-perforate, muri free, TEhI (Figs ) straight to winded, solitary or grouped, pattern gradually diminishing and disappearing towards the colpi and merging Sexine composed of a complete, distinctly sculptured and into the margo, apocolpium 5 distinctly rugulate to almost perforated tectum, a coarsely granular subtectal layer, and a psilate, with scattered perforations. distinct sole (foot-layer). Tectum comparatively thick, Figs Puliiirirr liermleyarw. (1) Polar view (Farges s.n., P), LM x (2) Equatorial view (Farges s.n., p), - Lhl x (3) Equatorial view (Farges sm., P), LM, x (4) Equatorial view (Farges s.n., P), LM x (5) Polar view (Farges s.n., P), SEM, x2500. (6) Polar view (Fang 157, P), SEM, x2500. (7) Equatorial view (Fang 157, P). SEM, x2500. (8) Detail of the apocolpium, showing distinctly rugulate sculpturing (Fang 157, P)!_SEJ$.x (9) Detail of the colpus region, showing the rather low colpus margin and smooth to coarsely granular colpus membrane (Fang 157, P), SEM, x (10) Close-up of the mesocolpium showing rugulate exhe sculpturing (Fang 157, P), SEM, x (1 1) Detail of exine sculpture near the apocolpium, showing elongated, straight to Winding, often branched muri (Fang 157, P), SEM, x Crana 35 (1996)

4 Pollera of Pcllitirtu 349 Grana 35 ( 1996)

5 350 C. Scliirareizd ranging between pm in the centres of the mesocolpia, tectum surface variously undulated to almost plain, boundary between tectum and subtectal elements rather indistinct, granular layer pm thick, granules heterogeneous, foot-layer pm thick. Nexine (endexine) distinctly developed, about pm thick, boundary between footlayer and nexine and proximal surface of the nexine - +coarsely granular. SPECIFIC POLLEN DESCRIPTIONS Prrliirnrs liernsleyrrnzrs Rehd. ex Schirarend & Olabi (Figs. 1-11) La1 (Figs. 1-4) Pollen mostly oblate-spheroidal, P (17-25) pm, E (19-28) pm, FI ( ), polar view triangular, mesocolpia straight to slightly convex, apocolpium 5-7 pm in diameter, equatorial view subrhomboidal, with *distinctly protruding equatorial caps, endoaperture lalongate, 1-4 x2-6 pm, exine 1-2 pm thick, stratification non-discernible, LO-pattern densely perforate. SERI (Figs. 5-11) Colpi' comparatively wide, equatorially slightly widened, colp:s margin 1- distinctly projected, variously notched, colpus ends mostly rounded, rarely pointed, colpus membrane coarsely granular, rarely psilate. Exine sculpture densely rugulate, muri rounded, psilate, about 0,5 jun thick and up to 4 pm long, straight to winding, often irregularly branched or more rarely in diversely sized aggregates of up to 8 parallel elements, variously undulating and interwoven with each other, exine pattern gradually diminishing towards the colpi, transforming into a poorly developed, weakly rugulate to coarsely granular margo, sculpture of the apocolpia distinctly rugulate, pattern without striking differences but appearing slightly flattened in comparison with the mesocolpia. Afrrteriul stirdied CHINA: Hupeh, Henry 6379 (GH). Kiangsi, Tsiang 9746 (W); Szechuan, Farges s.n. (P); Fang 157 (P). P. lzirszrtirs Hemsl. (Figs ). LRI (Figs ) Pollen suboblate to oblate-spheroidal, P (17-21) jun, E 22 (19-24) pm, FI ( ), polar view triangular, mesocolpia straight to slightly convex, apo- colpium 5-7 pm in diameter, equatorial view elliptic, endoaperture lalongate to elliptic, 2-4 x 3-7 pm, exine 1-2 ~irn thick, stratification non-discernible, LO-pattern loosely punctate. SEA4 (Figs ) Colpi narrow, equatorially slightly widened, colpus margin rather low, colpus ends mainly pointed, colpus membrane coarsely granular. Exine sculpture fossulate-perforate, perforations solitary in funnel-shaped depressions or grouped in &elongated, straight to slightly winding, slit-like depressions. Pattern gradually diminishing towards the colpi and apocolpia, merging into the psilate, scarcely perforated margo and apocolpia. hfuferiul stirdied CHINA - Kiangsi: Chung 42 (A); Anhwei; Ching 2744 (A). VIETNAM: Tonkin, Balansa 3978 (P). P. orietzfrrlis (Franchet) Hemsl. (Figs ) LnI (Figs ) Pollen suboblate to oblate-spheroidal, P (16-22) pm, E (18-24) pm, FI ( ), polar view triangular to subtriangular, with straight to slightly convex mesocolpia, apocolpium 4-6 pm in diameter, equatorial view elliptic, endoaperture lalongate to elliptic, diameter 2-4 x 3-6 pm, exine 1-2 pm thick, stratification nondiscernible, LO-pattern densely perforate. SEhI (Figs ). Colpi narrow, equatorially slightly widened, colpus margin slightly projected, variously notched, colpus ends pointed to rounded, colpus membrane coarsely granular. Exine sculpture densely rugulate, muri rounded, psilate, about 0,3-0,5 pm thick and up to 5 pm long, straight to winding, rarely branched, variously undulating and intenvoven with each other, often in aggregates of up to 6 parallel elements, Exine pattern gradually diminishing towards the colpi, equatorially transformed into a poorly developed, inconspicuously rugulate to +coarsely granular margo, towards the poles extending up to the colpus margin. Sculpture of the apocolpia distinctly rugulate, without any differences or demarcation against the mesocolpia, tectal perforations non-discernible. hfuterial studied CHINA: Yunnan, Henry 9427 (A) 8; Delavay 239 (P) & Forrest (W). Szechuan, Schneider 1433 (A). P. ruriiosissiriiirs (Lour.) Poir. (Figs ) Figs Puhrrrs Itirsurrrs. (12) Polar view (Chung 42, A), Lhl, x 1000, (13) Polar view (Chung 42. A), Lhl, x (14) Equatorial view (Balansa 3978, P), LM, x (15) Equatorial view (Balansa 3978, P), Lhl, x (16) Polar view (Ching 2743, A), SEhf, x (17) Equatorial view, showing the almost unsculptured apocolpium and the variously notched colpus nlargin (Ching 2743, A), SEM, x (18) Equatorial view (Ching 2743, A), SEhl x (19) Detail of the apocolpium, showing almost unsculptured tectum surface and pointed ends of the colpi (Ching 2744, A), SEhI. x $000. (20). Detail of the colpus region, showing a rather narrow colp~s and variously notched colpus margin (Ching 2744, A), SEM, x (21) Oblique view of the mesocolpium, showing the fossulate-perfonte exine sculpture and the markedly developed, unsculptured margo (Ching 2743, A). SEM. x (22) Detail of the mesocolpium showing fossulatr-perforate (cerebroid) exine sculpturing (Ching 2741, A), SEM, x Grana 35 ( I9Y6)

6 Pollen of Pnlirrrrrs 351 Gram 35 (1996)

7 352 C Scliirarend (For description see page 355). Gram 35 (I 996)

8 Pollen of Paliiiriis 353 (For description see page 355). Gram 35 ( 1996)

9 354 C. Schirarertd

10 ~i\l (Figs ) pollen suboblate to oblate-spheroidal, P (16-22) pm, E (20-25) pm, FI ( ), polar view triangular, mesocolpium straight to slightly concave, apocolpium 5-8 pm in diameter, equatorial view subrhomboidal to elliptic, endoaperture lalongate to elliptic, 2-4 x 3-6 pm, exine 1-2 pm thick, stratification non-discernible, LO-pattern perforate. sehi (Figs ). colpi narrow, equatorially slightly widened, colpus margin slightly projected, variously notched, rarely almost straight, colpus ends pointed, rarely rounded, colpus membrane coarsely granular around the apertures to almost psilate towards the poles. Exine sculpture fossulate-perforate (cerebroid), composed of elevated, rounded ridges and narrow, elongated or rounded depressions, ridges 2-3 pm thick and up to 6pm long, diversely shaped and orientated, psilate, depressions mainly very narrow, slit-like, straight to curved, sometimes branched, rarely up to 5pm long, with loosely scattered perforations. Exine pattern gradually diminishing and disappearing towards the colpi and apocolpia, merging into a psilate, scarcely perforated margo and psilate apocolpia. Marerial Stirdied CHINA: Fukien, Chung 6456 (A); Chung 2792 (A). JAPAN: Tokyo, Matsumura s.n. (UPS, BHU-PM). TAIWAN, Oldham 68 (W), Oldham s.n. (W). P. spiria-cliristi Mill. (Figs ) LhI (Figs ) Pollen oblate-spheroidal to prolate-spheroidal, P (17-28) pm, E (19-29) [im, FI ( ), polar view triangular, with straight to slightly convex mesocolpia, apocolpium 4-7 pm in diameter, equatorial view subrhomboidal, with slightly protruding equatorial caps. Pollen of Palirrrirs 355 Endoaperture lalongate, 1-5 x 2-6 pm. Exine 1-2 pm thick, stratification non-discernible, LO-pattern +densely perforate. SEhI (Figs ) Colpi comparatively narrow and shallow, colpus margins not projected, variously notched, colpus ends mainly pointed, colpus membrane poorly developed, coarsely granular. Exine sculpture densely rugulate, muri rounded, psilate, about 0,3-0,5 pm thick and up to 3 pm long, straight to winding, solitary or rarely in diversely sized and orientated aggregates of up to 8 parallel elements, often branched, variously undulating and'interwoven with each other. Pattern slightly diminished but not distinctly altered towards the colpi, margo not developed. Sculpture of the apocolpia distinctly rugulate, without any differences or demarcation against the mesocolpia, tectal perforations non-discernible. Muterial stirdied SPAIN. Bourgeau 499 ( W). CROATIA. Bierbach s.n. (A); Ronniger s.n. (W). DALMATIA. Ascherson s.n. (W); Witting 1320 (W). MAKEDONIA. Krendl s.n. (W); Adamovic 1320 (W). SERBIA. Bornmiiller s.n. (A); Vent s.n. (BHU). ROMANIA. Dobrogea, Paun 445 (UPS); Nyarady & Borza 571 (W). BULGARIA. Quasdorf 4992 (B). GREECE: Lokris; Mattfeld 2636 (A). DISCUSSION In accordance with the general morphological pattern of the family Rhamnaceae, pollen grains of the genus Paliirrrrs are uniformly isopolar, radially symmetrical, 3-(zono)-colporate and angulaperturate, with polar axes of I8 25 (16-28) pm and equatorial diameters of (18-29) pm. Moreover the five species agree in having comparatively long colpi, extending over about 4/5 of the polar axis and comparatively small apocolpia, with diamefers between 3-6(-8) pm. The apertures consist of a colpate ectoaperture and a +narrow lalongate to elliptic endoaperture, surrounded by +distinct, laterally opened and meridionally f elongated nexine thick- Figs Pulirrrrcs orientalis, Delavay s.n. (P). (23) Polar view, Lhl, x (24) Polar view, showing parasyncolporate aperture configuration, Lhl, x (25) Equatorial view, LM, x (26) Equatorial view, Lhl, x (27) Polar view, SEhl, x2500. (28) Equatorial view, SEM, x (29) Equatorial view, SEM, x (30) Detail of the apocolpium, showing rugulate to striate. exine sculpturing and the pointed ends of the colpi, SEM, x (31) Detail of the colpus region. showing the rather low and variously notched colpus margin and the poorly developed margo, SEhl, x (32) Detail of the mesocolpium showing rugdate exine sculpturing, SEhl, x (33) Detail of exine sculpture near the apocolpium, SEhl, x Figs. U-45. Pulitrrus rumosissinrtrs. (34) Polar view (Chung 6456, A), Lhl, x (35) Polar view (Fan & Li 47, A), Lhl, x (36) Equatorial view (Muroi 751, A), Lhl, x (37) Equatorial view (Chung 6356, A), Lhl, x (38-39) Section of the pollen wall showing a thick, +distinctly sculptured and sparsely perforated tectum, a granular subtectal layer and foot-layer (Matsumura sen., BHU-Phl), TEhl, ~ (40) Polar view (Oldham 68, A), SEhl, x (41) Equatorial view showing a narrow, equatorially iridened colpus (Oldham 68, A), SEhl, x (42) Detail of the apocolpium (Oldham 68, A), SEhl, x (43) Detail of the colpus region, showing a low colpus margin, poorly developed margo and a granular colpus membrane (Fan & Li 47, A), SEhl, x (44) Detail of exine sculpture near the apocolpium (Oldham 68, A), SEhl, x (45) Close-up of the mesocolpium, showing rugulate to fossulateperforate exine sculpturing (Muroi 751, A), SEhl, x Figs Pulirrrm spbra-chisti. (46) Polar view (Keller s.n., W), Lhl, x (47) Polar view (Keller sm, W), Lhl, x (48) Equatorial view (Krendl s.n., W), Lhl, x (49) Equatorial view (Adamovic 1320, W), Lhl, x (50) Polar view (Balansa s.n., P), SEhf, x2500. (51) Polar view (Balansa s.n., P), SEhl, x2500. (52) Equatorial view (Balansa s.n., P), SEhl, x2500. (53) Detail of the apocolpium showing rugulate exine sculpturing and pointed ends of the colpi (Balansa s.n., P). SEhI, x (54) Detail of the colpus region showing a low margin, poorly developed margo and a coarsely granular colpus membrane (Balansa s.n., P), SEhl, x5000. (55) Oblique view of the mesocolpium showing rugulate exine sculpturing (Balansa s.n., P), SEhI, x (56) Close-up of the mesocolpium showing the densely rugulate exine sculpture (Balansa s.n., P), SEhl, x Graria 35 ( 1996)

11 356 C. Scliirarerid enings (costae transversale). The exine is uniformly between 1-2 pm thick, lacking a distinct stratification under the light microscope. Exine sculpture ranges between +finely rugulate and fossulate-perforate corresponding to the Lasiodisciistype (P, henislejaittrs. P. orientalis and P. spiiia-cliristi) and Sageretia-type (P. hirsirtirs and P. rariiosissinnrs) established by Schirarend & Kohler (1993). This general pattern emphasises the affinities between Pnliirrtrs and the closely related genus Ziz@htrs Mill. Despite the general infrageneric uniformity certain differences and trends may be recognized in terms of pollen size and shape, and tectum architecture. With respect to such characters as fruit morphology, leaf morphology and wood anatomy, in Palitrnrs (Schirarend & Olabi 1991) these trends show a distinct west-east orientation corresponding to the distribution of the species. In pollen morphology, the less advanced pattern is always represented by the European- West Asian P. spina-cliristi, with comparatively large, mostly spheroidal grains of about pm diameter and densely rugulate exine sculpture covering the total grain including the apocolpia. Most similar to P. spiiia-cliristi are P. orieritalis and P. heriisle~aiiirs of Southern Central and Southeastern China. P. orieritalis exhibits oblate-spheroidal pollen with slightly reduced diameters of pm, a rugulate exine sculpture and distinctly sculptured apocolpia. The palynological similarity of P. spiiia-cliristi and P. orientalis corresponds very well with the general morphological resemblance of tbese closely allied species. P. heiilslejanirs which is found from Southeastern to Southern Central China, has rugulate exine sculpturing, distinctly sculptured apocolpia and pollen diameters of x pm and is somewhat intermediate between the two former species and P. rariiosissirinrs and P. hirsirtirs from Southeastern China, Japan, Korea, and Vietnam. According to the general trend of the Rhamnaceae for a successive fusing and levelling of the sculptural, supratectal elements (Schirarend & Koliler 1993), these two species show a rather advanced fossulate-perforate (cerebroid) exine architecture. The individual muri are +completely levelled and fused with each other forming almost psilate tectal areas of irregular shape and size surrounded by slit-like, straight to curved of this trend has been achieved by P. r~rnosissiini~s with comparatively small, suboblate grains, fossulate-perforate exine sculpture and psilate apocolpia. ACKNOWLEDGEMENTS I am very much indebted to the Directors and Curators of the various herbaria cited for providing polliniferous material. Moreover my thanks go to the Director and the staff of the Palynological Laboratory of the Swedish Museum of Natural History in Stockholm, especially to Mrs. E. GrafstrZjm for her skilful help with the TEM. I would also like to thank Mrs. M. Luchow and Mrs. J. Ueckert of the Botanical Garden and Botanical Museum Berlin- Dahlem for valuable technical assistance. REFERENCES El-Ghazaly, G. A Pollen flora of Qatar. - AiO Print Ltd., Odense. Faegri, K. & Iversen, J Textbook of Pollen Analysis. 4th ed., John Wiley & Sons, London. Hideux, hl. & Ferguson, I. K The stereostructure of the exine and its evolutionary significance in Saxifragaceae s. 1. in: Ferguson, I. K. & Muller, J. (Eds.) The Evolutionary Significance of the Exine. - Academic Press, London & New York. Horoivitz, A. & Baum, B Palynologie Mediterraneenne et Occidentale. 10. The arboreal pollen flora of Israel. -Pollen et Spores 9: Huang, T. C Pollen flora of Taiwan.-National Taiwan University. Botany Department Press, Taipei. Nilsson, S. & Muller, J Recommended palynological terms and definitions. - Grana 17: Nilsson, S. & Praglowski, J. (Eds.), Erdtman s Handbook of Palynology. Munksgaard, Copenhagen. Papagiannes, E Pollen studies of selected genera of Rhamnaceae.- Unpublished master s thesis, University of Illinois, Chicago. Praglowski, J. & Raj, B On some pollen morphological concepts. - Grana 18: Punt, W., Blackmore, S., Nilsson, S. & Le Thomas, A Glossary of pollen and spore terminology.-laboratory of Palaeobotany and Palynolog contributions series No. 1, Utrecht. Schirarend, C. & Kohler, E Rhamnaceae. - In: Nilsson, S. (ed.) World Pollen and Spore Flora. 17/18: Schirarend, C. & Olabi. M. N Revision of the genus Paliurus Toum. ex Mill. (Rhamnaceae).-Botanische depressions with scattered perforations.. The ultimate point Systematik Jahrbficher fir Grana 35 (1996)