Seed morphology of the paleotropical tribe Paropsieae (Passifloraceae, Malpighiales), and paleobotanical implications

. The fossil record of the diverse subfamily Passifloroideae (>750 species and 17 genera) is relatively poor. Despite the distinctiveness of its leaves (glandular and often emarginate), most of the fossils from this group have been described from seeds. Fossil seeds have been recovered from Europe, and North and South America. A lack of information on seed morphology for all the genera and tribes of this subfamily has prevented a tribe-level identification of the fossils and a better understanding of their biogeographic patterns. The Passifloroideae is divided into three tribes: Passifloreae with 10 genera, Paropsieae with six genera and the monotypic Jongkindieae. This study provides new descriptions for 15 species from 5 genera from the mostly Afrotropical tribe Paropsieae based on herbarium material, and introduces an online seed database and a key for 100 species of Passifloroideae compiled from literature and direct observations. Our study shows a low morphological diversity among the seeds of Paropsieae in comparison to a much larger diversity within Passifloreae. Some rare morphologies are only present in Passifloreae and can be used to assign seeds to this tribe. Within the Paropsieae, Androsiphonia has seed that are very distinct from those in the other genera in the tribe and also from the rest of the subfamily. The genus Paropsia exhibits two main morphotypes, while the genera Barteria , Paropsiopsis and Smeathmannia have very similar seeds with a highly conserved morphology. These results suggest that living or fossil Paropsieae cannot be identified confidently based solely on seed characters.


Introduction
The passion fruit family Passifl oraceae Juss.ex.Roussel comprises four subfamilies: Passifl oroideae Burnett (Angiosperm Phylogeny Group 2003), historically considered Passifl oraceae s. str.( AngiospermThe tribe Passifl oreae comprises 10 genera, including the genus Passifl ora L., with over 500 species (Feuillet & MacDougal 2007;Krosnick et al. 2009Krosnick et al. , 2013)).The tribe is morphologically characterized by climbing herbaceous plants with tendrils (Feuillet & MacDougal 2007;Tokuoka 2012).The passion fruit is part of this clade and mainly corresponds to the fruit of Passifl ora edulis Sims (Morton 1987).The genus Passifl ora is by far the most extensively studied genus due to its signifi cant economic and ecological importance (e.g., Ulmer & MacDougal 2004).Plants from this tribe can be found in both paleotropical and neotropical environments, but only the genus Passifl ora is present in both geographic areas (Krosnick et al. 2013;Hermsen 2021).
The fossil record of the Passifl oroideae is poor (Martínez 2017).Some fossils are diffi cult to identify and could belong to other groups (Martínez 2017;Hermsen 2021).Fossilized leaves dating back to the Cretaceous period have been considered as belonging to the Passifl oroideae, but they lack the diagnostic petiolar gland, and their familial identifi cation has recently been questioned (Martínez 2017;Hermsen 2021Hermsen , 2023)).Similarly, attribution of fossilized pollen to the Passifl oraceae is considered ambiguous (Martínez 2017;Hermsen 2021) except for those reported from the Miocene of South America (Palazzesi et al. 2014;D'Apolito et al. 2021;Hermsen 2023).Fortunately, fossilized seeds can be confi dently identifi ed as belonging to Passifl oroideae thanks to the palisade structure of the seed coat and the ruminate ornamentation of the surface (Martínez 2017).Apart from Passifl ora appalachiana Hermsen (4.5 Ma), Passifl ora bulgarica (Palamarev)  and Passifl ora sulcatasperma Hermsen (4.5 Ma) (Hermsen 2021(Hermsen , 2023)), all species of fossilized seeds of Passifl oroideae that cannot be assigned to a particular extant genus of seeds have all been grouped under the fossil genus Passifl oroidesperma Martínez (Martínez 2017;Hermsen 2021).The oldest member of Passifl oroidesperma, P. sogamosense Martínez, dates back to the late Eocene (45-34 Ma;Martínez 2017).Therefore, fossilized seeds are the most numerous remains that are unambiguous, making these organs particularly important for understanding the biogeography and evolutionary history of the group.However, as demonstrated by the establishment of the genus Passifl oroidesperma, their taxonomic resolution below the genus level is often insuffi cient (Martínez 2017).
The seed morphology of the extant Passifl oreae has been extensively studied for the genus Passifl ora, particularly representatives from South America (e.g., MacDougal 1994;Mezzonato-Pires et al. 2017;Pérez-Cortéz et al. 2002;Pérez-Cortéz 2007) while the seed morphology of other genera of the tribe (e.g., Adenia Forssk.with 100 species) has not been the subject of much research (e.g., Perrier de la Bathie 1945; Ngumbau et al. 2017).Although the seed morphology is not used to defi ne modern genera or species (Feuillet & MacDougal 2007), it appears to be of great importance in the diagnosis of certain subgenera of the genus Passifl ora (Mezzonato-Pires et al. 2017;Hermsen 2021).Indeed, seeds of Passifl ora can diff er in ornamentation, size, apex shape, and base shape (e.g., Mezzonato-Pires et al. 2017).On the other hand, the seeds of Paropsieae have been poorly studied, with only the seed of Paropsia gabonica Breteler being illustrated (Breteler 2003).Up to now, Martínez (2017) provided the most complete overview of the seed morphology in the Paropsieae, but mostly based on incomplete descriptions of seeds from the literature and not providing illustrations of them.Martínez (2017) concluded that there are probably no diff erences between the seeds of the two tribes.However, given the current state of knowledge, it is still diffi cult to determine whether it is feasible to attribute fossil seeds of Passifl oroidesperma to one tribe rather than another, or if it is simply impossible to distinguish them based solely on the seed morphology.A distinction between the seed morphology of the tribes would help clarify affi nities of the fossils with extant Passifl oroideae.
The aim of this study is to remedy this lack of information on the morphology of the seeds of the tribe Paropsieae.The objectives are: (1) to assess whether it is possible to distinguish the seeds of Paropsieae from those of the Passifl oreae, (2) to study whether the seeds can be used in the diagnoses of the genera of Paropsieae and (3) to distinguish the species within the genera on the basis of the seeds.

Material sampled
Specimens were collected from the Paropsieae collection at the Herbarium of Paris in the Muséum national d'Histoire naturelle.A total of 892 herbarium sheets belonging to the subfamily were examined.Among these sheets, only 75 included seeds.Floras and taxonomic revisions of the tribe were used to validate the identifi cations of these specimens (Olivier 1871;Perrier de la Bathie 1945;Hutchinson & Dalziel 1952;Sleumer 1970;Breteler 1999Breteler , 2003;;de Vos & Breteler 2009).In total, 16 sheets were selected based on the quality of seed preservation, covering 5 out of 6 genera and 15 out of the 22 species in the tribe.Two seeds were selected per sampled sheet.The species Paropsia gabonica, described in 2003 (Breteler 2003), was not present in the collection but is still mentioned in the online database (see below) because there is an illustration of the seed (Breteler 2003).

Methods of study and descriptive nomenclature
The selected seeds were photographed using a Canon EOS 5DS camera equipped with an MPE65mm lens.The seeds were placed fl at under multidirectional lighting.Each seed was photographed from four aspects: a view of each face, a side view, and a basal view.The focal stacking was done using the stackshot device and Affi nity Photo and Designer software (ver.1.10) to combine the photographs.The seeds were then embedded in resin and cut to create thin sections in the laboratory following the protocol by Benedict (2015).The thin sections were observed under a Nikon Eclipse 80i optical microscope and a Hirox RH-2000 digital microscope, and photographs were taken at 4 × to 20 × magnifi cations.
The methodology for measuring the seeds and establishing the characteristics of ornamentation, shape, and structure of the margin, apex and base is based on Pérez-Cortéz et al. (2002) and Mezzonato-Pires et al. (2017), with modifi cations based on the descriptions by Hermsen (2021Hermsen ( , 2023)).All measurement were performed using ImageJ software (Rasband 2016).
The morphological data were recorded in an online database Xper3 (Ung et al. 2010;Kerner et al. 2021).
The key based on this database is available at: https://app.xper3.fr:443/xper3GeneratedFiles/publish/identifi cation/-5560928563158630166/.The database contains 116 species.In order to have a means of comparing the morphologies and diversity of Paropsieae to Passifl oreae, we have added in the database selected descriptions from the literature of the Passifl oreae genera Passifl ora, Deidamia Noronha ex Thouars, Ancistrothyrsus Harms and Adenia (Perrier de la Bathie 1945;de Wilde 1972;Jørgensen et al. 1987;MacDougal 1994MacDougal , 2001;;Gilbert & MacDougal 2000;Pérez-Cortéz et al. 2002, 2005, 2009;Pérez-Cortéz 2007;Jørgensen & Vásquez 2009;Vanderplank & Zappi 2011;Lozada-Pérez & Gutiérrez 2016;Mezzonato-Pires et al. 2017;Ngumbau et al. 2017;Espinoza et al. 2018;Feuillet 2020;Vanderplank & Ochoa 2020).In total, 100 species (91 species of Passifl ora, one species of Ancistrothyrsus, one species of Deidamia and seven species of Adenia) of the Passifl oreae were entered into the database.Another 15 species came from our study and one species from Breteler (2003).The database utilizes 15 descriptors: the degree of compression of the seed, general shape, ornamentation, appendage on the apex, base shape, mucro presence, margin, length, width, thickness, width/thickness ratio, number of reticulations per mm 2 , reticulation diameter, reticulation depth, totaling 23 character states.We converted the average and deviation values from the study of Pérez-Cortéz et al. (2002) to ranges.The literature is inconsistent in describing the general shape, calling the same shape as "elliptical", "oblong", or "obovoid".We consider these diff erences as insignifi cant for our purpose and describe the general shape in such cases as "elliptic to oblong".The descriptors for reticulation dimensions and reticulation number are dependent on the ornamentation and are not applicable to the smooth ornamentation state.The database comprehensively covers the Paropsieae (Supp.fi le 2) but the Passifl oreae are less complete because the reticulation dimensions and wall thickness are mostly not specifi ed in the literature.

Results
An overview of the morphological diversity of the Paropsieae studied here is given in Table 1.
The palisade seed coat structure is the same for all the following seeds except for Androsiphonia, and we have illustrated the character only once in Fig. 1F.

Seed description
Seeds are ca 6.0-9.0 mm long, 6.0-8.0 mm wide and 5.0-5.5 mm thick, oblong to nearly circular, wider than thick.The surface is completely smooth, dark brown, with visible hairy tegument.The apex is blunt, rounded with a small depression.The base is rounded.The margin is entire.The integuments are reduced to a single cellular layer.

Seed description
Seeds compressed, 4.6-7.0mm long, 3.0-4.0mm wide and 1.8-2.2mm thick, curved oblong.The surface is coarsely reticulate, with an average of 4.00 reticulations per mm 2 .The reticulations have an average diameter of 630 μm and a depth of 170 μm.The margin is entire.The apex lacks a prominent appendage.
The base is acute and truncate, bearing a mucro.The palisade seed coat is on average 135 μm thick.

Remark
The genus is represented by 4 species, 3 are studied here.

Seed description
Seeds compressed, 5.0 mm long, 3.0 mm wide and 2.0 mm thick, curved oblong.The surface is coarsely reticulate and black, with an average of 4.50 reticulations per mm 2 .The reticulations have an average diameter of 634 μm and a depth of 159 μm.The margin is entire with a fold.The apex lacks prominent appendages.The base is acute and truncate, with a mucro.The palisade seed coat is 135 μm thick on average.

Seed description
Seeds compressed, 7.0 mm long, 4.0 mm wide and 2.0 mm thick, curved oblong.The surface is coarsely reticulate and black, with an average of 3.68 reticulations per mm 2 .The reticulations have an average diameter of 818 μm and a depth of 231 μm.The margin is entire.The apex lacks a prominent appendage.The base is acute and truncate, with a mucro.The palisade seed coat is 161 μm thick on average.

Seed description
Seeds compressed, 4.9-8.1 mm long, 2.9-7.0 mm wide and 1.3-2.7 mm thick, oblong or cordate, sometimes curved.The surface is reticulate-foveolate or coarsely reticulate, with an average of 5.60 reticulations per mm 2 .The reticulations have an average diameter of 487 μm and a depth of 190 μm.
The margin is striate or entire, sometimes with a lateral fold.The apex may have a prominent appendage.
The base is obtuse or acute, sometimes truncate, and may have a mucro.The palisade seed coat is on average 230 μm thick.

Remark
The genus is represented by 12 species, 8 are studied here.

Seed description
Seeds compressed, 7.5 mm long, 5.2 mm wide and 2.6 mm thick, oblong.

Seed description
Seeds compressed, 7.1 mm long, 5.8 mm wide and 2.4 mm thick, cordate.The surface is coarsely reticulate and light brown, with 7.12 reticulations per mm 2 .The reticulations have an average diameter of 414 μm and a depth of 188 μm.The margin is striate.The apex has a prominent appendage.The base is obtuse and truncate, with a mucro.The palisade seed coat is 281 μm thick.

Seed description
Seeds compressed, 5.3 mm long, 3.0 mm wide and 1.5 mm thick, cordate.The surface is coarsely reticulate and brown, with 6.25 reticulations per mm 2 .The reticulations have an average diameter of 268 μm and a depth of 99 μm.The margin is striate.The apex lacks prominent appendages.The base is obtuse and truncate, with a mucro.The palisade seed coat is 122 μm thick.

Seed description
Seeds compressed, 5.0 mm long, 2.9 mm wide and 1.4 mm thick, oblong.The surface is reticulatefoveolate and light cream, with 6.12 reticulations per mm 2 .The reticulations have an average diameter of 458 μm and a depth of 173 μm.The margin is entire with a very pronounced fold.The apex lacks a prominent appendage.The base is acute, with a mucro.The palisade seed coat is 221 μm thick.

Seed description
Seeds compressed, 7.5 mm long, 6.9 mm wide and 2.0 mm thick, cordate.The surface is coarsely reticulate and light cream, with 7.62 reticulations per mm 2 .The reticulations have an average diameter of 589 μm and a depth of 277 μm.The margin is striate.The apex lacks any appendages.The base is obtuse, without a mucro.The palisade seed coat is 243 μm thick.

Seed description
Seeds compressed, 7.0 mm long, 5.5 mm wide and 2.4 mm thick, cordate.The surface is coarsely reticulate and light cream, with 4.62 reticulations per mm 2 .The reticulations have an average diameter of 361 μm and a depth of 238 μm.The margin is striate with a lateral fold.The apex has a prominent appendage.The base is obtuse, with a mucro.The palisade seed coat is 234 μm thick.

Seed description
Seeds compressed, 7.7 mm long, 6.3 mm wide and 2 mm thick, cordate.The surface is coarsely reticulate and light cream, with 3.75 reticulations per mm 2 .The reticulations have an average diameter of 675 μm and a depth of 188 μm.The margin is striate.The apex has a prominent appendage.The base is obtuse, without a mucro.The palisade seed coat is 214 μm thick.

Seed description
Seeds compressed, 5.9-6.1 mm long, 2.6-2.9 mm wide and 1.6-1.9mm thick, oblong.The surface is reticulate foveolate and brown, with an average of 6.12 reticulations per mm 2 .The reticulations have an average diameter of 195 μm and a depth of 106 μm.The margin is entire.The apex lacks a prominent appendage.The base is acute and truncate, with a mucro.The palisade seed coat is 103 μm thick.

Seed description
Seeds compressed, 4.6-5.2mm long, 3.0-3.7 mm wide and 1.6-1.8mm thick, oblong.The surface is reticulate foveolate, with an average of 9.50 reticulations per mm 2 .The reticulations have an average diameter of 236 μm and a depth of 121 μm.The margin is entire.The apex lacks prominent appendages.The base is obtuse, truncate, and has a mucro.The palisade seed coat is on average 155 μm thick.

Remark
The genus is represented by 7 species, 2 are studied here.

Position of Androsiphonia
The seed morphology in the genus Androsiphonia diff ers from the other genera of the tribe Paropsieae and is also very distinct among all other seeds of Passifl oroideae.As the only non-compressed seed, it is completely smooth, without reticulation, and has a wide oblong shape, almost circular.Its surface is covered with a hairy tegument that is absent in all other seeds of the family.The appearance of the apex is very distinctive: it is recessed, and the rest of the seed folds over it.The seed coat structure is also completely diff erent.While all other genera have seeds with a palisade seed coat, Androsiphonia is covered with a single layer of isodiametric cells.Androsiphonia seems to be the only genus in Passifl oroideae that has lost the palisade structure.Even though its seed does not resemble a Passifl oroideae seed, the genus Androsiphonia is confi dently placed within the Passifl oroideae in phylogenies and studied fl oras (Stapff 1904;Feuillet & MacDougal 2007;Tokuoka 2012). Schmelzer & Gurib-Fakim (2008) described the seed of Androsiphonia as "Seed with pitted wall, surrounded by pulpy aril".This succinct description was not supported by any illustration.There seems to be no misidentifi cation in the herbarium of Paris (see Supp. fi le 1), which includes most of the vegetative characters we expected to fi nd.The leaves have a pair of glands in the basal part, are broad and toothed with six to eight pairs of secondary veins (Hutchinson & Dalziel 1952), and the fruit is characteristic of Passifl oroideae (Supp.fi le 1).The studied plates are also very consistent with the collection of plates associated with this genus, which can be consulted via the GBIF aggregator (https://www.gbif.org/fr/occurrence/gallery?taxon_key=7313531).Until now, the seed has never been illustrated.It is therefore conceivable that Androsiphonia has extremely derived seeds among the Passifl oraceae.Pollen of Androsiphonia is also very distinct compared to the other types of pollen present in the Passifl oroideae (Mezzonato-Pires et al. 2022).Thus, Androsiphonia appears to be a particularly derived genus within the Passifl oroideae.

Comparison of the tribes Passifl oreae and Paropsieae
The tribes Passifl oreae and Paropsieae are separated by molecular and vegetative morphological criteria (Feuillet & MacDougal 2007;Tokuoka 2012).The tribe Passifl oreae is highly diverse and exhibits several seed morphological characters that are absent in the tribe Paropsieae (Supp.fi le 2).For example, seeds with sulcate or scrobiculate ornamentation are only found in Passifl ora (Supp.fi le 2).Similarly, the seed of Passifl ora microstipula L.E.Gilbert & J.M.MacDougal is unique in having the winged margin (Gilbert & MacDougal 2000).Several species of Passifl ora also have dentate, crested or fractioned margin, very diff erent to what we fi nd in the Paropsieae (Supp.fi le 1).The genus Dilkea Mast.also has seeds distinguishable from others: the seeds are large with a smooth to pustulate surface (Hermsen 2021).The tribe Paropsieae exhibits much lower morphological diversity compared to the Passifl oreae.
Excluding the genus Androsiphonia, only two forms (oblong and cordate), two types of ornamentation (reticulate-foveolate and coarsely reticulate), and two types of margin (entire and striate) are present in Paropsieae.These are also the most common morphologies in the Passifl oreae (Supp.fi le 2).It appears that the morphological diversity of the Paropsieae is contained within the morphological space of the Passifl oreae, as previously stated by Martínez (2017).Thus, it is not possible to identify a seed as belonging to the tribe Paropsieae, as its morphological equivalent will be found in Passifl oreae, except for the genus Androsiphonia.

Comparison of the genera within the Paropsieae
Within the Paropsieae, the seeds of diff erent genera have relatively similar morphologies but with some marked diff erences (Table 1).Two major morphological categories can be distinguished: one with an elongated oblong seed, entire margin, and apex without an appendage (morphotype 1), and one with a wide and fl at cordate seed, coarsely reticulate ornamentation, striate margin, and obtuse base (morphotype 2).Morphotype 1 is present in the genera Barteria, Paropsia, Paropsiopsis, and Smeathmannia.Morphotype 2 is only found in Paropsia, representing the majority (six out of eight) of the studied species.The genera other than Paropsia each have only one morphology, meaning that, apart from Paropsia, all seeds within the same genus have the same ornamentation.Only in Paropsia do we fi nd coarsely reticulate and reticulatefoveolate seeds.The genera Barteria, Paropsiopsis, and Smeathmannia have very similar morphologies and all bear a basal mucro (Table 1).The genera Smeathmannia and Barteria are sometimes considered synonymous (POWO 2023) and are phylogenetically sister taxa (Tokuoka 2012).The phylogeny by Tokuoka (2012) separates Paropsia from the rest of the Paropsieae and places Smeathmannia and Barteria together in one clade, along with Androsiphonia.However, the study did not include Paropsiopsis due to a lack of available specimens (Tokuoka 2012).Smeathmannia and Barteria are also grouped together in a clade in the morphological classifi cation by Feuillet & MacDougal (2007).The study of the seed morphology suggests that Paropsiopsis is part of the Smeathmannia-Barteria-Androsiphonia clade and confi rms the close relationship between Smeathmannia and Barteria, as, apart from ornamentation, the seeds are very similar in their shape (curved oblong), margin (entire with a fold) and base with a mucro.
No trends linking the genera to the seed size could be observed, as they are all within the same order of magnitude.The genera (except Androsiphonia) do not possess unique diagnostic characters, but certain species of Paropsia have unique combinations of characters that allow them to be separated from other genera.Since the genera of this tribe often occur in the same geographical areas (Olivier 1871; Perrier de la Bathie 1945; Hutchinson & Dalziel 1952;Sleumer 1970, Breteler 1999, 2003;de Vos & Breteler 2009), knowledge of the seed morphology can, in some cases (e.g., cordate shape), indicate the genus within the tribe.

Comparison at the species level
The genus Barteria exhibits particularly conserved morphology.All studied seeds of the genus are oblong, slightly curved, with reticulation of crests and an entire margin with a pronounced fold on one side, as well as very similar apex and base shapes.This is the only genus with more than two species where there are no variations in seed morphology among species.Therefore, it is impossible to distinguish species within this genus based on the seed shape.
The genus Paropsia is the only one that comprises two morphotypes.Paropsia brazzaeana and P. grewioides belong to morphotype 1 and exhibit reticulate foveolate and coarsely reticulate ornamentation, respectively.
All other seeds belong to morphotype 2. Paropsia brazzaeana displays an atypical morphology of its seed with a very thick, almost vertical margin and a hooked-horn apex.Its resemblance to other seeds of morphotype 1 is purely superfi cial and primarily based on its shape.On the other hand, P. grewioides stands out for its strong resemblance to a Barteria seed with its reticulate-foveolate ornamentation.They share the same characteristics of the shape, apex, base, and margin.The cordate morphotype seeds resemble each other greatly, with P. edulis, P. obscura, and P. madagascariensis being particularly similar and distinguishable only by their dimensions and the number of reticulations.Apart from the apex, all seeds of morphotype 2 share the same characteristics, except for P. vareciformis which has a highly curved cordate shape.It is also the only Asian species in the tribe, found in Malaysia (Kiew et al. 2018).Therefore, it is possible to distinguish two morphotypes within Paropsia, but it remains challenging to diff erentiate species based on seed morphology.
The genus Smeathmannia comprises only two species: Smeathmannia laevigata and S. pubescens.The seeds of both species have very similar morphology and only diff er in their curvature.Due to the limited number of samples, we cannot exclude that this diff erence can be due to intra-specifi c variation.

Paleobotanical implications
The genus Passifl oroidesperma contains fossil seeds that can only be confi dently identifi ed at the subfamily level (Martínez 2017).There are three extant tribes: Jongkindieae is at the base of the sub-family and is a sister group of both Passifl oreae + Paropsieae (Breteler et al. 2022).The tribe Jongkindieae has seeds very distinct from those of Passifl oroidesperma.The seed surface of Jongkindieae is tuberculate and the seed wall has a corrugated testa (Breteler et al. 2022).Passifl oroidesperma is characterized by a seed surface foveolate, coarsely foveolate, reticulate-foveolate or transversally grooved, and the seed coat made of prismatic palisade cells (Martínez 2017;Hermsen 2021).These characteristics, although very diff erent from Jongkindieae, are found in the Passifl oreae and Paropsieae as shown in this study.Thus, Passifl oroidesperma should be placed at the node that includes Passifl oreae and Paropsieae and excludes Jongkindieae.
Fossil seeds with the morphological characteristics of the Paropsieae should be placed in Passifl oroidesperma as their defi nitive attribution to an existing tribe is impossible based solely on their morphology.On the contrary, fossil seeds possessing characters such as sulcate or scrobiculate ornamentation and winged, dentate, crested or fractioned margin should be at least placed in the Passifl oreae.Within Passifl oreae, some combinations of characters allow fossils to be placed at the genus or subgenus level (Hermsen 2021(Hermsen , 2023)), but the lack of knowledge of some genera (e.g., Adenia, Basananthe Peyr, Crossostemma Planch.ex.Benth., Efulensia C.H.Wright, Mitostemma Mast.and Schlechterina Harms, POWO 2023) remains an unresolved obstacle to a better taxonomic accuracy in this tribe.

Conclusion
This study has documented several seed morphologies in the tribe Paropsieae, thereby fi lling a gap in the taxonomic knowledge of the subfamily Passifl oroideae.We have found that the separation between Passifl oreae and Paropsieae is challenging to accomplish based solely on the seed morphology because the morphological space occupied by seeds of the Passifl oreae includes the less diversifi ed morphospace occupied by the Paropsieae.Only the seed of the genus Androsiphonia is distinctive enough to be assigned to the Paropsieae.Therefore, in certain cases, it is possible to assign a fossil seed to the tribe Passifl oreae or a genus rather than to just the subfamily.At the level of the tribe Paropsieae, it is practically impossible to diff erentiate between the genera Paropsiopsis and Smeathmannia based on seed characteristics.Within the genus Barteria, it is impossible to distinguish between diff erent species based on seeds.Paropsia is the only species-rich genus where it is possible to identify particular morphotypes and potentially identify a species based on the seed morphology.The genus Androsiphonia is particularly atypical, and its seeds are very distinct from the others in the tribe.
As a perspective, it should be noted that the vast majority of Passifl oreae seeds come from the study of the genus Passifl ora, while the other genera (e.g., Adenia, Basananthe, Crossostemma, Efulensia, Mitostemma and Schlechterina; POWO 2023) which have an African or African-Asian distribution are poorly documented.The absence of a detailed phylogeny of the tribe is also a limitation to our study.It has been impossible to link the diff erent morphotypes to the evolutionary history of the group and determine the plesiomorphic state of seed morphology in the Paropsieae.While it can be assumed that the oblong seed with an entire margin found in Passifl oreae represents the plesiomorphic condition, a complete phylogenetic study of Paropsieae is needed to draw defi nitive conclusions.

Table 1 .
Comparisons of the 5 genera belonging to the tribe Paropsieae studied herein.
Hook.f.Seeds compressed, 4.7 mm long, 3.0 mm wide and 1.8-2.2mm thick, curved oblong.The surface is coarsely reticulate and cream, with an average of 4.75 reticulations per mm 2 .The reticulations have an average diameter of 634 μm and a depth of 159 μm.The margin is entire with a lateral fold.The apex lacks a prominent appendage.The base is acute and truncate, with a mucro.The palisade seed coat is 105 μm thick on average.
The surface is reticulatefoveolate and orange-brown, with 3.87 reticulations per mm 2 .The reticulations have an average diameter of 720 μm and a depth of 213 μm.The margin is entire and very thick.The reticulations bordering the margin are open laterally.The apex has a hooked prominent appendage.The base is obtuse, without a mucro.The palisade seed coat is 275 μm thick.
Seeds compressed, 7.3 mm long, 6.4 mm wide and 1.8 mm thick, curved cordate.The surface is coarsely reticulate and light cream, with 5.37 reticulations per mm 2 .The reticulations have an average diameter of 411 μm and a depth of 164 μm.The margin is striate with a lateral fold.The apex has a prominent appendage.The base is obtuse and truncate.The palisade seed coat is 228 μm thick.
The reticulate-foveolate surface is yellow-brown, with 7.62 reticulations per mm 2 .The reticulations have an average diameter of 245 μm and a depth of 108 μm.The margin is entire with a lateral fold.The reticulations bordering the margin are open laterally.The apex lacks prominent appendages.The base is obtuse and truncate, with a mucro.The palisade seed coat is 156 μm thick.Seeds compressed, 5.1 mm long, 3.6 mm wide, and 1.7 mm thick, oblong.The reticulate-foveolate surface is light brown, with 8.50 reticulations per mm 2 .The reticulations have an average diameter of 231 μm and a depth of 135 μm.The margin is entire.The apex lacks prominent appendages.The base is obtuse and truncate, with a mucro.The palisade seed coat is 154 μm thick.