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Pollen morphology of Xyridaceae (Poales) and its systematic potential.

Xyridaceae (Poales) are a predominantly tropical and subtropical family of five genera and about 415 species (Kral, 1998; Campbell, 2004a; 2008). The family is most speciose in South America where the greatest number of Xyris species occur, especially on the Brazilian (160 spp.) and Guiana (90 spp.) shields, and four of the genera are endemic: Abolboda (23 species.), Achlyphila (one species), Aratitiyopea (one species), and Orectanthe (two species) (Kral, 1998; Campbell, 2004b, 2008).

Xyris Gronov. ex L. (1753) and Abolboda Humb. (1813) have long taxonomic histories; however, two-thirds of the currently recognized species of Abolboda, as well as three Xyridaceae genera, were not named until the last half of the twentieth century (see Campbell, 2008). These relatively enigmatic genera had been considered morphologically disparate (Suessenguth & Beyerle, 1935; Rudall & Sajo, 1999) and great differences in pollen morphology were emphasized to treat them as two families (Nakai, 1943, see Samuelsson in Nilsson & Praglowski, 1992) or subfamilies (Suessenguth & Beyerle, 1935; Takhtajan, 2009, see also Thorne & Reveal, 2007). Xyridoideae (Xyris) were circumscribed with unifacial leaves; ellipsoid, sulcate pollen; orthotropous ovules; and ellipsoid seeds (Dahlgren et al., 1985; Kral, 1998). In contrast, Abolbodoideae (Abolboda, Aratitiyopea, and Orectanthe) have bifacial leaves, spherical pollen without an evident aperture, novel glands on the gynoecium, anatropous ovules, and spherical seeds (Dahlgren et al., 1985; Kral, 1998; Campbell, 2004b; Campbell & Stevenson, 2007). Achlyphila (Maguire & Wurdack, 1960) obscures this division in sharing characters with both subfamilies (e.g., unifacial leaves and spheroidal pollen grains; Dahlgren et al., 1985; Kral, 1998). Additionally, this monotypic genus presents features unique in the family, such as its inflorescence architecture and a persistent abaxial sepal (Dahlgren et al., 1985; Kral, 1998; Campbell, 2004b, 2005; Campbell & Stevenson, 2007). Despite the morphological diversity, Xyridaceae (s. lat.) are generally considered monophyletic (Stevens, 2001; Thome & Reveal, 2007; APG III, 2009; Takhtajan, 2009), which has been substantiated by phylogenetic analyses of molecular datasets (Chase et al., 2006, and references therein) and morphological and anatomical research on previously little known taxa (e.g., Campbell, 2004b, 2005; Campbell & Stevenson, 2007). However, infrafamilial treatments differ (Stevens, 2001; Thorne & Reveal, 2007; Takhtajan, 2009).

Palynological research on Xyridaceae is hindered by limited suitable samples, especially in fluid preserved collections, due to the remote locations of most populations and the brief floral phenology (Carlquist, 1960; Campbell, 2004b). The most extensive study of Xyridaceae pollen (Appendix) was conducted by Carlquist who examined whole and sectioned grains using light microscopy (LM). Differences in shape, pollen wall ornamentation, and grain size were found to be taxonomically informative (Carlquist, 1960), and the need to further characterize Xyridaceae pollen with respect to familial circumscription was highlighted (Erdtman, 1963). Relatively few investigations of Xyridaceae have presented data from scanning electron microscopy (Campbell, 2004b; Campbell & Stevenson, 2007; Hesse et al., 2009). Because pollen of Xyris is thus far considered to be relatively uniform, and that of other Xyridaceae diagnostic at the generic and possibly lower taxonomic ranks (Carlquist, 1960; Campbell, 2004b), this study emphasizes Xyridaceae with spherical, apparently inaperturate pollen with the aim of assessing pollen characters of potential taxonomic usefulness.

Materials and Methods

Pollen from species representing all Xyridaceae genera were examined (Table 1) from samples obtained from dehisced herbarium specimen anthers or from liquid preserved specimens housed at the New York Botanical Garden (fixed in FPA and later transferred to 70% ethanol; Johansen, 1940). Acetolysis and treatment with NaOH are known to dissolve the exine of Xyridaceae pollen (Erdtman, 1952; Carlquist, 1960), thus only untreated grains were examined. Pollen was transferred to specimen mounts and ethanol from wet collections was evaporated under ambient conditions. Preparations were coated with gold palladium in a Hummer 6.2 sputtering system (Anatech, Union City, CA, U.S.A). Observations were made with a JEOL JSM-5410LV (JEOL, Tokyo, Japan) scanning electron microscope (SEM) at 10 kV and digital images were acquired using Orion software (JEOL, Tokyo, Japan). Measurements were made on SEM images using Carnoy 2.0 software (Schols & Smets, 2001). Measurements are averages of several grains except in the case of insufficient samples (Abolboda egleri, A. grandis var. rigida, A. neblinae, A. paniculata, Achlyphila disticha); diameters exclude ornamentation. Only grains that appeared fully formed were measured except for A. macrostachya var. robustior in which the grains were collapsed. Measurements are provided for comparative purposes and should not be treated as exact as in both this study and the literature pollen treatments have varied. As noted by Carlquist (1960), precise measurements of Xyridaceae pollen are probably only possible on fresh grains. Palynological terminology follows Punt et al. (1994), the term "clypeate" follows Halbritter and Hesse (1995), and size classes follow Hesse et al. (2009). Table 1 lists the information on specimens used in this research and Table 2 summarizes pollen external morphology including measurements from literature (see Appendix).

Pollen Descriptions of Xyridaceae

Abolboda. Pollen grains large to very large, 49-180 [micro]m in diameter, spheroidal, and inaperturate (Table 2, Fig. 1; Erdtman, 1952; Carlquist, 1960). Pollen wall ornamentation is spinose with either verrucae (Fig. 1a, b, c, d, e, f and g, I-k) or pila (Fig. 1h and 1) in the interspinal areas (Carlquist, 1960). Spines 2.65-12.0 [micro]m long (Table 2; Erdtman, 1952), usually obconical, often with a swollen base (Fig. 1d, e, g, h, i and j, and k; Erdtman, 1952; Carlquist, 1960), or sometimes tapered (Fig. 1k); gemmae often at the base (Fig. lj). Spines distally rounded, obtuse, occasionally approaching clava (Fig. 1l), or acute (Fig. lk).

Achlyphila. Pollen grains medium, 22-34 [micro]m in diameter, spheroidal, and clypeate (Table 2, Fig. 2f; Maguire & Wurdack, 1960; Carlquist, 1960). Pollen wall covered with large, irregular shields of pila with narrow to wide, unornamented, recessed spaces between the shields.

Aratitiyopea. Pollen grains large to very large, 81-195 [micro]m in diameter, spheroidal, and inaperturate (Table 2, Fig. 2a, b and c; Nowicke in Steyermark, 1984; Campbell, 2004b; Campbell & Stevenson, 2007). Pollen wall ornamentation is very large clavae, clavae often swollen distally, interspersed in a matrix of similarly shaped, finer and smaller clava (Fig. 2b).

Orectanthe. Pollen grains very large, 105-250 [micro]m in diameter; the largest likely occur in O. ptaritepuiana (based on measurements in Carlquist, 1960). Grains are spheroidal and inaperturate (Table 2, Fig. 2d, e; Maguire, 1958; Carlquist, 1960). Pollen wall ornamentation is large clavae, clavae often distally swollen, basally sometimes constricted, sometimes with gemmae or short clava-like projections, interspersed in a matrix of finer and smaller clavae (Table 2, Fig. B, C; Carlquist, 1960).

Xyris. Pollen grains medium to large; the longest axis 32-70 [micro]m (Sharma, 1968; Ybert, 1979). Grains elliptic, flattened or convex in lateral view (van Zinderen Bakker, 1953; Straka & Friedrich, 1984; Rudall & Sajo, 1999) to occasionally irregular (Lisowski et al., 2001) or subspheroidal (Huang, 1970). Pollen grains mono- (Erdtman, 1952; van Zinderen Bakker, 1953; Sharma, 1968; Huang, 1970; Ybert, 1979) or bi-sulcate (Erdtman, 1952; Straka & Friedrich, 1984; Cruz-Barros et al., 2000); trisulcate grains questionably reported (X. rupicola Kunth; Erdtman, 1952). Pollen wall ornamentation is reticulate or finely reticulate (van Zinderen Bakker, 1953; Sharma, 1968; Ybert, 1979; Cruz-Barros et al., 2000) and punctate (Sharma, 1968), or foveolate (Sharma, 1968; Straka & Friedrich, 1984).

Results and Discussion

Two main patterns of pollen morphology are present in Xyridaceae: spheroidal grains without an evident aperture, and pollen walls ornamented with projections, and elliptical, sulcate grains with fine wall ornamentation. Pollen morphology is diagnostic for genera; however, amongst those with spheroidal grains morphological characters appear do not to be as reliable for circumscribing lower taxonomic ranks as previously thought. Pollen in Xyridaceae is liable to alteration (see also Carlquist, 1960) and variation in grain size and other harmomegathic effects due to ambient conditions effecting moisture, and preservation and preparation techniques. For example, fluid preserved grains of Achlyphila were 33% larger (Table 2) than air dried pollen grains, whereas the great size range in a single species of Aratitiyopea (81-195 [micro]m) were measured from similarly preserved but differently analyzed material. Air dried pollen grains that are subsequently rehydrated were mostly found to be unsuitable for SEM (unpubl. data). Pollen grain diameters observed from SEM preparations were consistently smaller than those reported from LM studies (Table 2), most notably in taxa with the largest pollen grain diameters (Abolboda macrostachya, Aratitiyopea, and Orectanthe). Sunken exine elements and ridges (Fig. 2d, e), previously reported as muri (Campbell, 2004b), are interpreted as preparation artifacts (see also Carlquist, 1960).

Pollen wall ornamentation of most Abolboda species is verrucate with dispersed spines (Table 2). Overall spine shape (Carlquist, 1960), and particularly that of the base (Erdtman, 1952), that were considered diagnostic of species and infraspecific taxa, are not proving as consistent with examination of additional material. Variation in the morphology and width of spine bases occurs within a pollen grain (Fig. ld) and within (Carlquist, 1960) or between flowers of a species (e.g., A. pulchella [Erdtman, 1952: Fig. 259B, C], including synonymous A. vaginata [Smith & Downs, 1968; Campbell, 2005]). Short pila observed here in A. linearifolia (Fig. 1h) were not present in the NaOH treated sample examined by Carlquist (1960). The clava-like spines and longer pila present in A. grandis var. rigida, one of the largest Abolbodas, resemble the pollen wall ornamentation in the larger-flowered genera Aratitiyopea and Orectanthe. Pollen grains of Aratitiyopea and Orectanthe are densely covered with large, conspicuous projections (visable at 10x, pers. obs.) and grains of Orectanthe are amongst the largest in Angiosperms (Mabberley, 2008). Further evaluation of these latter genera, each comprising two taxa, is needed to determine if pollen morphology is infragenericaly informative. Pollen morphology supports the hypothesis that populations of A. lopezii var. lopezii disjunct on the Guiana Shield and the Cordillera del Condor represent the same entity (Campbell, 2004b, 2008).

Clypeate pollen occurs in several unrelated Angiosperm families (Halbritter & Hesse, 1995), and in Xyridaceae is thus far known only in Achlyphila. In this pollen class, germinating tubes emerge from between the exine shields (Halbritter & Hesse, 1995). Clypeate grains are either functionally omniaperturate and have a thin exine and uniformly thickened intine (Thanikaimoni, 1986; Furness & Rudall, 1999, 2000) or are porate with localized thickenings of intine (Chanda & Ghosh, 1976; Halbritter & Hesse, 1995). A thin exine and thick intine were revealed by LM examination of Abolboda and Aratitiyopea (Carlquist, 1960, Nowicke in Steyermark, 1984). Within Monocots species with superficially inaperturate pollen grains are associated with wet habitats (Furness & Rudall, 2000) and those within Xyridaceae occur in habitats with high levels of, often episodic, precipitation.

Pollen morphology has been examined in only a small percentage of Xyris species; however, the size range and pollen wall ornamentation appear to be more uniform than in Abolbodoideae (s. str.: Abolboda, Aratitiyopea, and Orectanthe) species so far examined. Fully formed elliptical and irregularly shaped undeveloped grains have been observed from the same anther in Xyris (Newman 143 (NY), unpubl, data) and it is likely that reports of spheroidal or irregularly shaped grains were based on poorly formed material.

Conclusions and Future Perspectives

Observations of pollen morphology using scanning electron microscopy further distinguish the genera of Xyridaceae. Within the genera possessing apparently inaperturate pollen, the utility of pollen characters in circumscribing lower taxonomic groups is hampered due to limited samples that are difficult to comparatively assess due to harmomegathic effects. Population based studies of Abolboda, the most species rich genus in this pollen class, would give insight into infraspecific variation. Pollen morphological characters alone do not support circumscribing Achlyphila as Xyridoideae, and are being examined in a phylogenetic context along with other structural and molecular characters (Campbell et al. in prep.). As this investigation progresses, pollen will be characterized for major lineages of Xyris, which will enable testing the hypothesis that fully formed pollen grains of Xyris are elliptic.

Acknowledgments A portion of this work was completed for my dissertation and I am grateful to Dennis Stevenson for his mentorship and support during the research. Numerous individuals and organizations provided logistic support for collecting in Venezuela, and I thank G. A. Romero and H. van der Werff for samples. Field work was supported by funding from The Explorers Club Exploration Fund, New York; The Fund for Neotropical Plant Research of The New York Botanical Garden; the International Association for Plant Taxonomy, and the City University of New York.


Table 3 Palynological references for Xyridaceae (a)

Taxon                                           Reference

Abolboda acaulis Maguire                        Carlquist, 1960

Abolboda bella Maguire                          Carlquist, 1960

Abolboda ebracteata Maguire & Wurdack

var. brevifolia Maguire (as A. acicularis       Carlquist, 1960
Idrobo & L. B. Sm)

var. ebracteata                                 Carlquist, 1960

Aboloba grandis Griseb.

var. guayanensis Maguire (= A. grandis var.     Carlquist, 1960

var. rigida Malme                               Campbell 2004b

Abolboda linearifolia Maguire                   Carlquist, 1960,
                                                Campbell 2004b

Abolboda macrostachya Spruce ex Malme

var. angustior Maguire                          Carlquist, 1960

var. macrostachya                               Carlquist, 1960

var. robustior Steyerm.                         Carlquist, 1960

Abolboda paniculata Maguire                     Campbell 2004b

Abolboda poarchon Seub.                         Kuprianova, 1948;
                                                Erdtman, 1952

Abolboda pulchella Humb.                        Erdtman, 1952,
                                                Campbell 2004b

Abolboda sprucei Malme                          Carlquist, 1960

Achlyphila disticha Maguire & Wurdack           Carlquist, 1960;
                                                Maguire & Wurdack,
                                                1960 Campbell 2004b

Aratitiyopea lopezii (L. B. Sm.) Steyerm.
& P.E. Berry

var. lopezii                                    Nowicke in Steyeanark,
                                                1984, Campbell 2004b,
                                                Campbell & Stevenson,
                                                2007; Hesse et al.,

Orectanthe Maguire                              Maguire, 1958

Orectanthe ptaritepuiana (Steyerm.) Maguire     Carlquist, 1960

Orectanthe sceptrum (Oliv.) Maguire             Malme, 1933;
                                                Carlquist, 1960,
                                                Campbell 2004b

Xyris anceps Lam.                               Straka & Friedrich,
                                                1984; Lisowski et al.,
                                                2001, Campbell 2004b

Xyris anisophylla Welw. ex Rendle               Lisowski et al., 2001

Xyris aristata N.E. Br.                         Lisowski et al., 2001

Xyris bampsii Lisowski                          Lisowski et al., 2001

Xyris capensis Thunb.                           Erdtman, 1952; Sharma,

Xyris capillaris Malme                          Lisowski et al., 2001

Xyris caroliniana Walter                        Erdtman, 1952

Xyris congensis Buttner                         Lisowski et al., 2001

Xyris decipiens R. Br.                          Ybert, 1979

Xyris dihingensis Brylska                       Lisowski et al., 2001

Xvris dissimilis Malme                          Lisowski et al., 2001

Xvris erubescens Rendle                         Lisowski et al., 2001

Xvris foliolata L.A. Nilsson                    Lisowski et al., 2001

Xyris formosana Hayata                          Huang, 1970, 1972

Xyris friesii Malme                             Lisowski et al., 2001

Xyris frondosa Maguire & L. B. Sm.              Salgado-Labouriau &
                                                Villar de Seoane, 1992

Xyris fugaciflora Rendle                        Lisowski et al., 2001

Xvris humilis Kunth                             Straka & Friedrich,

Xvris imitatrix Malme                           Lisowski et al., 2001

Xyris jupicai Rich.                             Cruz-Barros et al.,

Xyris kornasiana Brylska & Lisowski             Lisowski et al., 2001

Xyris kundelungensis Brylska                    Lisowski et al., 2001

Xyris leonensis Hepper                          Lisowski et al., 2001

Xyris lepotphylla Malme                         Lisowski et al., 2001

Xyris obscura N.E. Br.                          Ybert, 1979

Xvris obtusiuscula L.A. Nilsson                 Rudall & Sajo, 1999

Xyris pauciflora Willd.                         Govindapa, 1956

Xyris rupicola Kunth                            Erdtman, 1952

Xyris sanguinea Malme                           Lisowski et al., 2001

Xyris savanensis Miq.                           Cruz-Barros et al.,

Xyris schizachne Mart.                          Cruz-Barros et al.,

Xyris scabridula Rendle                         Lisowski et al., 2001

Xyris smalliana Nash                            Erdtman, 1952

Xyris teres L.A. Nilsson                        Cruz-Barros et al.,

Xyris tortula Mart.                             Cruz-Barros et al.,

Xyris umbilonis L.A. Nilsson                    van Zinderen Bakker,

Xyris wallichii Kunth                           Sharma, 1968

Xvris sp. (as "alpestris", ined.)               von Mohl, 1834

Xyris sp. (as "eriantha", ined.)                von Mohl, 1834

(a) Nomenclature follows Campbell (2005, 2008)

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DOI 10.1007/s12229-012-9110-7

Lisa M. Campbell (1,2)

(1) The New York Botanical Garden, Bronx. NY 10458. USA

(2) Author for Correspondence; e-mail:

Published online: 10 October 2012

Table 1 Xyridaceae Specimens investigated in this study

Country of origin, voucher, and voucher location are followed by
(l.p.) or (h) to indicate that liquid preserved or dried herbarium
specimen material, respectively, was examined.

Abolboda acicularis Idrobo & L. B. Sin., Venezuela: Campbell et al.
667, NY (l.p.)

Ab. americana (Aubl.) Malme ex Lanjouw, Venezuela: Romero & Gomez
3392, VEN (l.p.) Surinam: Maguire & Stahel 23666, NY (h)

Ab. bella Maguire, Venezuela: Huber 4804, VEN, (h)

Ab. ciliata Maguire & Wurdack Venezuela: Luteyn et al. 9424, NY,
(h) Ab. ebracteata vat. brevifolia Maguire Venezuela: Romero s.n.,
NY, (h)

Ab. ebracteata Maguire var. ebracteata, Venezuela, Maguire &
Steyermark 34516, NY, (h)

Ab. egleri L. B. Sin. & Downs, Brazil: Plowman 9714, F, (h)

Ab. grandis Griseb. vat. grandis, Venezuela: Campbell et al. 637,
NY, (l.p.)

Ab. grandis Griseb. var. rigida Malme, Venezuela: Maguire 23148,
NY, (h)

Ab. granularis (Maguire) L. M. Campb. & Kral, Venezuela: Campbell
et al. 625, NY, (l.p.)

Ab. linearifolia Maguire, Venezuela: Campbell et al. 653, NY (l.p.)

Ab. maerostachya Spruce ex Malme var. angustior Maguire, Venezuela:
Campbell et al. 651, NY, (1.p.) Ab. macrostachya Spruce ex Malme
var. macrostachya, Venezuela: Campbell et al. 510, NY, (l.p.) Ab.
maerostachya var. robustior Steyerm., Venezuela: Campbell et al.
745, NY, (l.p.) Ab. minima Maguire Venezuela: Campbell et al. 621,
NY, (1.p.)

Ab. neblinae Maguire, Venezuela: Steyermark 103754, NY, (h)

Ab. paniculata Maguire, Venezuela: Steyermark 109328, NY, (h) Ab.
poarchon Seub. var. poarchon, Brazil: Irwin et al. 21947, NY, (h)

Ab. pulchella Humb., Venezuela: Campbell et al. 756, NY, (l.p.)

Ab. sprucei Maline, Venezuela: Campbell et al. 472, NY (l.p.)

Achlyphila disticha Maguire & Wurdack, Venezuela: Maguire et al.
42386, NY, (h)

Aratitiyopea lopezii (L. B. Sin.) Steyerm. & P. E. Berry var.
lopezii, Peru, van der Werff et al. 16131, MO, (l.p.); Venezuela,
Campbell et al. 813, NY, (l.p.)

Orectanthe sceptrum (Oliv.) Maguire, Venezuela: Campbell et al.
789, NY, (l.p.)

Table 2 Pollen characters of Xyridaceae with inaperturate grains

Taxon                                 ([micro]m)

Abolboda acicularis                    59.9
Ab. americana                          53.6
Ab. bella                              86.0
Ab. ciliata                            66.1
Ab. ebracteata var. brevifolia         72.1
Ab. ebracteata var. ebracteata         55.3
Ab. egleri                             62.7
Ab. grandis var. grandis               74.7
Ab. grandis var. rigida               112.9
Ab. granularis                         66.1
Ab. linearifolia                       85.5
Ab. macrostachya var. angustior        67.9
Ab. macrostachya var.                  65.4
Ab. macrostachya vat. robustior        81.4
Ab. minima                             65.1
Ab. neblinae                           82.2
Ab. paniculata                         83.2
Ab. poarchon var. poarchon             86.0

Ab. pulchella                          66.4
Ab. sprucei                            54.7
Achlyphila disticha                    24.9
Aratitiyopea lopezii var. lopezii      88.5
O. sceptrum                           105.0

Taxon                                 ([micro]m)

Abolboda acicularis                    96 (a)
Ab. americana
Ab. bella                             110 (a)
Ab. ciliata                            96 (a)
Ab. ebracteata var. brevifolia         96 (a)
Ab. ebracteata var. ebracteata         90 (a)
Ab. egleri
Ab. grandis var. grandis
Ab. grandis var. rigida
Ab. granularis
Ab. linearifolia                      120 (a)
Ab. macrostachya var. angustior       155 (a)
Ab. macrostachya var.                 105 (a)
Ab. macrostachya vat. robustior       180 (a)
Ab. minima
Ab. neblinae
Ab. paniculata
Ab. poarchon var. poarchon            756 (b), 97.5-12 (c)

                                      105 (b)
Ab. pulchella                         105 (b)
Ab. sprucei                           120 (a)
Achlyphila disticha                   32 (a), 32-34
Aratitiyopea lopezii var. lopezii     175-195 (f)
Orectanthe                            160-250 (g)
O. sceptrum

Taxon                                 ornamentation

Abolboda acicularis                   spines & verrucae
Ab. americana                         spines & verrucae
Ab. bella                             spines & verrucae
Ab. ciliata                           spines & verrucae
Ab. ebracteata var. brevifolia        spines & verrucae
Ab. ebracteata var. ebracteata        spines & verrucae
Ab. egleri                            spines & verrucae
Ab. grandis var. grandis              spines & verrucae
Ab. grandis var. rigida               spines & pila
Ab. granularis                        spines& verrucae
Ab. linearifolia                      spines & pila
Ab. macrostachya var. angustior       spines & verrucae
Ab. macrostachya var.                 spines & verrucae
Ab. macrostachya vat. robustior       spines & verrucae
Ab. minima                            spines & verrucae
Ab. neblinae                          spines & verrucae
Ab. paniculata                        spines & verrucae
Ab. poarchon var. poarchon            spines & verrucae

Ab. pulchella                         spines & verrucae
Ab. sprucei                           spines & verrucae
Achlyphila disticha                   pila
Aratitiyopea lopezii var. lopezii     large & small clavae
O. sceptrum                           large & small clavae

                                      large exine
Taxon                                 elements

Abolboda acicularis                    3.63
Ab. americana                          3.12
Ab. bella                              3.06
Ab. ciliata                            5.05
Ab. ebracteata var. brevifolia         3.34
Ab. ebracteata var. ebracteata         4.81
Ab. egleri                             6.12
Ab. grandis var. grandis               8.12
Ab. grandis var. rigida               11.70
Ab. granularis                         7.79
Ab. linearifolia                       6.39
Ab. macrostachya var. angustior        7.42
Ab. macrostachya var.                  5.72
Ab. macrostachya vat. robustior        8.04
Ab. minima                             2.73
Ab. neblinae                           7.78
Ab. paniculata                         9.54
Ab. poarchon var. poarchon             3.97

Ab. pulchella                          4.64
Ab. sprucei                            4.20
Achlyphila disticha
Aratitiyopea lopezii var. lopezii      6.30
O. sceptrum                            5.65

(a) Carlquist, 1960

(b) Erdtman, 1952

(c) Kuprianova, 1948

(d) Malme, 1933

(e) Maguire & Wurdack, 1960

(f) Nowicke in Steyermark, 1984

(g) Maguire, 1958
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Author:Campbell, Lisa M.
Publication:The Botanical Review
Article Type:Report
Geographic Code:1USA
Date:Dec 1, 2012
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