Bull. Natl. Mus. Nat. Sci., Ser. B, 35(1), pp. 17–21, March 22, 2009

Morphological Study of Pseudopeltate Scales in Davallodes
hymenophylloides and Wibelia divaricata (Davalliaceae)
Chie Tsutsumi* and Masahiro Kato
Department of Botany, National Museum of Nature and Science, Amakubo 4–1–1, Tsukuba, 305–0005 Japan* Corresponding author: E-mail: tsutsumi@kahaku.go.jp

Abstract We studied the detailed cellular-level structure of the pseudopeltate scales of Davallodes hymenophylloides and Wibelia divaricata (Davalliaceae). Results revealed that the structuresof the pseudopeltate scales are complicated not only in the cellular contents but also in the shieldstructures. The developmental pattern of the pseudopeltate scale of D. hymenophylloides was similar to that of the peltate scales of other Davalliaceae and related ferns, suggesting a close phylogenetic relationship of the two scales.
Key words : Davalliaceae, fern, scale development, scale structure.

Introduction
In leptosporangiate ferns, the rhizomes areusually invested with trichomes, scales, or bothas dermal appendages. Scales are present in various taxa and are suggested to have arisen recurrently in the leptosporangiate ferns (Pryer et al.,1995). They are various in color and form (e.g.,thin or thick, clathrate or not, entire or toothed at
the margin, acuminate or obtuse at the tip, truncate, round or cordate at the base, basifixed,
pseudopeltate or peltate) and are commonly used
as taxonomic characters (Kramer and Green,1990).
Basifixed scales are attached by broad bases,
while peltate and pseudopeltate scales, composedof a shield and a stalk, are attached by cylindricalstalks perpendicular to the shields. In the peltatescale, the stalk is inserted near or below the center of the shield, while in the pseudopeltate scale,though it is apparently similar to the peltate
scale, the stalk is attached strictly at the base of
the shield and the shield proximal to the stalk iscordate and imbricate. Our previous study inferred that peltate and pseudopeltate scales,
which are common in several groups of ferns including epiphytes in the broad sense, have an
evolutionary linkage to the epiphytic life form in

the lineage leading to Davalliaceae and Polypodiaceae (Tsutsumi and Kato, 2008). Our studies
also suggested that morphological changes between peltate and pseudopeltate scales may haveoccurred multiple times, because both types ofscales are seen in the same genera in Davalliaceae and Polypodiaceae (Tsutsumi and Kato,2006, 2008).
Most previous systematic studies have focusedon the morphology of the scales and made grossmorphological observations (Nayar et al., 1968;
Sen et al., 1972; Kato, 1975, 1985). Our anatomical study of peltate and pseudopeltate scales in
Davalliaceae and related ferns (Tsutsumi andKato, 2008) revealed that there are variations in
the cellular-level and histological features andthe degree of stalk insertion into a rhizome concavity. The cells of the central part of the shieldaround the stalk vary from those containing cytoplasm to those lacking cytoplasm and having
thick walls, and to those having dense contents
particularly in the exterior zone of the shield. The
stalk of some species is attached to the flat rhizome, and other species have stalk deeply inserted into rhizome depressions. The detailed structure of pseudopeltate scales remains yet to be described because the scales are so complicated.
In this study, we report the detailed cellular-

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Chie Tsutsumi and Masahiro Katolevel structure and development of pseudopeltate
scales of Davallodes hymenophylloides (Blume)
M. Kato et Tsutsumi, (previousely called
Araiostegia hymenophylloides Blume) and thestructure of Wibelia divaricata (Blume) M. Katoet Tsutsumi (previousely called Davallia divaricata Blume) for better understanding the diversity of the scales in Davalliaceae.
Materials and Methods
Sources and vouchers of Davallodes hymenophylloides and Wibelia divaricata (Davalliaceae)
are shown in Table 1. Scales with rhizomes werecollected and fixed in FAA (formaldehyde : acetic
acid : 50% ethanol5 : 5 : 90). To observe scalestructure, portions of rhizomes about 5 cm apartfrom the apex were cut into 10–12-m m-thick sections using a sliding microtome (LEICASM2000R, Leica, Germany) on a freezing stand(MCR 802R, Komatsu, Kanagawa, Japan). Sections were embedded in a glycerol solution andsealed with nail polish.
To observe the development of scales of D. hymenophylloides, apices of rhizomes and leaves
were dehydrated in an ethyl alcohol series for approximately 2 h and embedded by HistoResin
Plus for 4 d (Leica, Heidelberg, Germany). The
Table 1.

embedded materials were cut into 2–5-m m-thicksections with a glass knife on an ultramicrotome(LEICA RM2155, Leica, Vienna, Austria). Sections were stained with safranin, toluidine blue,and orange G (Jernstedt et al., 1992).
Results
Anatomy of pseudopeltate scale
Selected serial longitudinal sections of apseudopeltate scale of Davallodes hymenophylloides by freezing microtomy showed that theposterior part of the shield was attached to theposterior side of the stalk but the middle of thestalk (Fig. 1). In a section of a periphery stalk,the structure of the scale looked like a peltate
scale with a stalk inserted in a shield (Fig. 1A).
In a submedian section on one side, the anteriorshield was double layered and the upper shield
was a continuation of the posterior shield, which
in turn was similar to a peltate structure (Fig.
1B). This structure was caused by a hooked endof the scale base, along which the shield was attached to the stalk (Fig. 2). As mentioned by
Tsutsumi and Kato (2008), serial sections
showed that the stalk and the central part of theshield comprised cells with cytoplasm and theother part of the shield was one cell thick andSource and voucher of species examined in this study

Species

Source/voucher

Davallodes hymenophylloides (Blume) M. Kato et Tsutsumi
Wibelia divaricata (Blume) M. Kato et Tsutsumi

Gunung Salak, Java, Indonesia; IN89
Cibodas, Java, Indonesia; IN27Fig. 1. Selected serial sections of pseudopeltate scale of Davallodes hymenophylloides. The rhizome apex islocated to right. A. Section at periphery of stalk. B. Near middle. C. Middle. Scale bar100 m m.

Pseudopeltate scales of Davalliaceae

devoid of cytoplasm. The stalk was short and located in a nearly flat or a very shallow depressionof the rhizome.
The pseudopeltate scale of Wibelia divaricata
was similar to that of D. hymenophylloides in thatthe posterior part of the shield was attached tothe posterior side of the stalk except for the middle (Fig. 3). This scale, however, was different
from that of D. hymenophylloides in that the anterior shield had a posterior projection and wasalways single layered thorough serial sections inFig. 2. Diagram of pseudopeltate scale of Davallodes hymenophylloides. Lines A–C indicate
sectioning positions in Fig. 1. The stalk isshown in gray, and the connection of stalk andshield is indicated by thick broken line.

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this study (Fig. 3). The stalk was composed ofvery small cells and prominently sunken in a
deep concavity of the rhizome. Cells of the shieldnear the stalk were dead and consisted mostly ofcell walls (Fig. 3; Tsutsumi and Kato, 2008).
Development of Pseudopeltate scale in Davallodes hymenophylloides
The early development of the pseudopeltate
scale was quite similar to that of the peltate
scales of Nephrolepis cordifolia (L.) C. Presl(Lomariopsidaceae) and Davallia trichomanoides
Blume (Davalliaceae) (Figs. 2C–F and 3 in Tsutsumi and Kato, 2008). One-cell layered scales
were produced near the rhizome apex and leaf
primordia by oblique and then by transverse cell
divisions (Figs. 4A–C). The basal part of thescale, or an initial stalk, underwent cell divisions
longitudinally and transversely to become a stalkconsisting of multiple rows of cells (Figs. 4D–E).
Selected serial sections showed that the cordate
posterior part of the shield was formed in thesubmedian and lateral parts of the stalk by cell
divisions of the dorsal cells, which were derived
from subdeltoid subbasal cells (Fig. 4E), whereas
no or few cell divisions occurred in the middle
on the posterior side (Fig. 4D). In the course ofscale development, there was no remarkablechange in the epidermis and outer cortex of therhizome (Fig. 4A). It differed from the developmental pattern of D. trichomanoides, in which
the epidermis and outer cortex of the rhizome
around the scale gave rise to deep concavities bydifferential growth as the stalk elongated (Tsut-Fig. 3. Selected serial sections of pseudopeltate scales of Wibelia divaricata. The rhizome apex is located toright. A. Section at periphery of stalk. B. Near middle. C. Middle. Arrowheads indicate shields of neighboring scales. Scale bar100 m m.

20Chie Tsutsumi and Masahiro Kato

Fig. 4. Longitudinal sections of young pseudopeltate scales at different developmental stages in Davallodes
hymenophylloides. The rhizome apex and leaf primordium (LP) are located to left. A. Different stages ofscales. B. Enlarged scale initial with oblique division. C. Young one-cell layered scale. D–E. Selected serial
sections of more developing scale. D. Median section showing absence of subdeltoid subbasal cell (portion
marked by solid arrowhead). E. Submedian section near edge of stalk, showing subdeltoid subbasal cells.
Scale bar100 m m.

sumi and Kato, 2008).
Discussion
Our results showed that the cellular-levelstructures of the pseudopeltate scales are more
complicated than those expected by a gross morphological study (Kato, 1975). The pseudopeltate
scale of Davallodes hymenophylloides had double-layered anterior parts of the shield, the upperof which was caused by the hooked end of thebase of the posterior shield. The upper anteriorshield covered the stalk and lower anterior shield,
and appears to protect the stalk and the shield,
whose cells are alive. In Wibelia divaricata, theanterior part of the shield was always observed tohave a projection at the base. The projection also
covered the stalk and may protect the stalk of living cells. In contrast, peltate scales of otherDavalliaceae and related ferns had thick-walledshield cells around the stalk, except the scale of
Arthropteris beckleri (Hook.) Mett. (Tsutsumiand Kato, 2008).

Pseudopeltate scales of Davalliaceae

The developmental pattern of the posteriorshield of pseudopeltate scales in D. hymenophylloides was similar to that of the peltate scales ofNephrolepis cordifolia and Davallia trichomanoides (Tsutsumi and Kato, 2008). Although there was no developmental data, theupper anterior shield of the pseudopeltate scale
may be a result of a prominent growth of one ofthe posterior shield lobes in association with ahooked base of the shield. It is suggested that thepseudopeltate scales are similar to the peltate
scales in developmental mechanisms. It has noinconsistency against the hypothesis that theshifts between peltate and pseudopeltate scales
may have occurred multiple times.
Acknowledgments
We thank D. Darnaedi, G. G. Hambali and T.
Ng. Praptosuwiryo for helping us collect materials in Indonesia. We are also indebted to Dr. R.
Imaichi for technical information and allowing touse facilities in her lab. This study was supportedby a Grant-in-Aid for Scientific Research fromthe Japan Society for the Promotion of Science.
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