A Reconsideration of the Genus Pityrogramma
(Adiantaceae) in Western North America
P.O. Box 299, St. Louis,
Botanik der Technischen
The silverback and goldback ferns of the genus Pityrogramma Link are
graceful plants of small to medium size, well known to fern fanciers
their beautiful white to yellow farinose indument. Tryon & Tryon (1982)
classified the group in the tribe Taenitideae of their broadly circumscribed
Pteridaceae Reichb. (= Adiantaceae (C.
see Pichi Sermolli, 1986)
and the taxa were last revised taxonomically by Tryon
who recognized 14
Among the goldback and silverback
ferns, the complex of species indigenous
to the southwestern United States and adjacent
Mexico has excited the greatest
controversy, both with respect to species number and affinities of the group.
Tryon (1962) followed Weatherby's (1920) disposition of the taxa as four
varieties of a single species, P. triangularis (Kaulf.)
Maxon. Alt & Grant
however, recognized three distinct species based on Weatherby's varieties, P.
pallida (Weath.) K. &
V. Grant, P. viscosa (D. Eaton) Maxon, and P. triangularis
(with only two varieties). The California Flora (Munz &
Keck, 1968) followed the
single species scheme in the general text, but recognized three species in the
supplement, and also included mention of two other varieties of P. triangularis
described since the work of Alt &
At the generic level there has been growing
that the southwestern
complex is anomalous within Pityrogramma.
Tryon (1962) pointed out that this
group departs in several morphological characters
from the relatively uniform
"central group" of species in the genus and suggested that this specialized
relative of Pityrogramma proper might merit generic recognition. He chose to
treat the taxa as a single genus, however, to emphasize the similarities (rather
than the differences) between the groups. More
recently, Tryon &
suggested that the southwestern complex might be better classified in the tribe
than the tribe
but postponed formal
until the group's
affinities became better known.
studies leading to treatments
the genus Pityrogramma
of North America Project and the Ferns and Fern Allies of the Southwestern
United States (Windham
we also concluded that the P.
triangularis complex should be segregated
This paper is
intended to review the rationale for distinguishing these two morphologically
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VOLUME 80 NUMBER 1 (1990)
convergent groups and to supply the new nomenclatural combinations
necessary to accommodate
To those familiar with Pityrogramma, the southwestern P. triangularis
complex appears amply distinct from the remainder
of the genus. Tryon (1962)
emphasized that while both groups are characterized
by farinose fronds, the P.
triangularis complex possesses several features unique in the genus. Rhizome
scales of the latter are
bicolorous, with strongly
and thin, hyaline margins. In Pityrogramma proper the rhizome scales are
concolorous or at best with a somewhat darkened, poorly defined central
portion. Stipes of the southwestern complex are terete
and contain one vascular
bundle, but typical Pityrogramma species possess adaxially sulcate stipes with
two (sometimes more) vascular bundles. The lamina shape is strongly
in the western North American
specific epithet triangularis), but in the other species varies from linear to
lanceolate or occasionally deltate-lanceolate. Pinnae of members of the P.
triangularis complex are sessile or adnate,
whereas at least the lower pinnae of
tropical species are stalked and none are adnate. More
noted that members of the P. triangularis complex are unique in frequently
having catadromous venation (actually,
venation is catadromous above
of pinnae, which are
to their pinna apex, but appear anadromous
to the lamina apex),
while the remainder of the genus is distinctly anadromous.
Spores of the P. triangularis complex are unique in the genus (Tryon, 1962;
1982). Typical Pityrogramma
spores possess an equatorial
with 1-4 accessory, parallel ridges (Fig. 1). In addition, the spores are
bicolorous, with dark brown ridges over a tan matrix. Pityrogramma
R. Tryon and the P. triangularis
complex possess spores lacking ridges and
flanges (Fig. 2) and therefore appear uniformly brown. The former taxon
possesses spores that are finely granulate and almost entirely lacking
ornamentation. Taxa in the P. triangularis
complex all have coarsely
spores with more or less fused tubercles (Tryon
Tryon 1982). In this respect
they resemble species of the tribe Cheilantheae (which have spores lacking an
more than they do those of the tribe Taenitideae (almost
which have spores with an equatorial
knowledge of the cytology of Pityrogramma
is somewhat ambiguous,
to the disproportionate
number of inexact counts in the literature. Walker
counted five species, P. calomelanos (L.)
chrysophylla (Sw.) Link,
(as P. tartarea
P. sulphurea (Sw.) Maxon,
P. trifoliata (as Trismeria trifoliata (L.) Diels), but was able to achieve exact
counts for only the last two taxa, due to high ploidy levels in the others. He
indicated that P. sulphurea and the three ambiguous counts were based on
x = 30, but unfortunately provided no documentation to support this notion.
His count of n = 58 for P. trifoliata corrected
an earlier miscount of n = 60 by
YATSKIEVYCH ET AL.: PITYROGRAMMA
FIGS. 1-4. Spores and chromosomes of Pityrogramma and Pentagramma species. FIG. 1. Spores of
Pityrogramma ebenea (Yatskievych & Beetle 81-372), with equatorial flanges and otherwise
reticulate perispores. FIG. 2. Spores of Pentagramma triangularis subsp. maxonii (Windham &
Yatskievych 337), with tuberculate perispores, the tubercles irregularly fused. FIG. 3. Meiotic
chromosomes of Pityrogramma ebenea from Jamaica (Ranker & Trapp 856), with 2n= 116II. FIG. 4.
Meiotic chromosomes of Pentagramma triangularis subsp. maxonii (Windham & Yatskievych 337),
with 2n = 30II. All bars = 20 I.m.
Wagner (1963; note that Wagner was quoted by Walker (1966) as having
recounted his original material as n = 57-58). Several other counts for various
Pityrogramma species (mainly from Indian collections) exist in the literature,
based both on x = 29 and x = 30 (see Love, L6ve, & Pichi Sermolli, 1977), but
most are inexact counts lacking clear documentation.
Confusion concerning the chromosome base number of Pityrogramma sensu
stricto has been dispelled somewhat by focusing on recent, photographically
documented reports. Tryon et al. (1975) presented a well documented count of
n = 116 (x = 29) for P. calomelanos from Brazil, in disagreement with previous
counts for that species. Recent collections of P. ebenea from Estado Morelos,
Mexico (Windham, Yatskievych, & Ranker 520 [UT]) and St. Andrew Parish,
Jamaica (Ranker & Trapp 856 [UC]) yielded clear meiotic preparations with
2n = 116II (Fig. 3), contradicting Walker's (1966) earlier, inexact count for this
AMERICAN FERN JOURNAL:
VOLUME 80 NUMBER 1 (1990)
based on x = 29, rather than x = 30.
In contrast to the confusing cytological situation of tropical Pityrogramma
species, the situation in the P. triangularis
complex is relatively clearcut as to
All taxa examined thus far
have been based on x = 30. We present
here a first count of 2n = 3011 for the taxon traditionally referred to as P.
triangularis var. maxonii (Fig. 4), from Arizona (Cochise County, Windham &
Yatskievych 337 [ASC]).
The chromosomal data provide additional evidence
that the P. triangularis group is misplaced in the current
all other members of the tribe Taenitideae (apparently
sensu stricto) have a base number of x = 29. Instead,
the southwestern complex
may be placed more correctly within the Cheilantheae, where x = 30 is a
common base number.
The flavonoid exudates responsible for
farinas of the goldback
ferns have been studied in detail by a number
by Wollenweber, 1978). These farinose exudates are epicuticular, glandular
excretions composed primarily of complex mixtures of flavonoid aglycones
(commonly chalcones, flavonols, flavones, and related classes of compounds).
Wollenweber & Dietz (1980) presented
a review of the taxonomic distribution of
such compounds in the 14 species included by Tryon (1962) in Pityrogramma.
They found that members of the P. triangularis
none of the 8
common constitutents that characterize all of the other 13 species of
Pityrogramma (but see Wollenweber et al. (1985), for discussion of a single,
anomalous sample of P. triangularis
containing compounds normally found in
Pityrogramma). Instead, the southwestern taxa produce as major farina
constituents compounds not found in any other
Pityrogramma species. Only in
their trace constituents do the southwestern taxa
overlap slightly with the rest of
In light of these morphological, cytological, and phytochemical data, it does
not seem at all probable
that the complex of southwestern species traditionally
treated as Pityrogramma
are merely a specialized group within that genus. As
suggested by Tryon
the affinities of the complex may be with the
Cheilantheae, rather than Taenitideae. Even if one accepts a position for the P.
triangularis complex within the Taenitideae, it is clear that this distinctive
complex should not be classified with Pityrogramma
proper and deserves
at the generic level.
Much research is still necessary to refine generic affinities within the
and even Pityrogramma
sensu stricto contains
detailed by Tryon (1962), two further anomalous
species have been classified in
the genus. The first,
(L.) Diels), is a widespread neotropical species that has subdimorphic, linear
fronds with 1-3(-7)-foliolate pinnae and finely granulate spores lacking an
equatorial ridge. Its farina, however, consists of "typical" Pityrogramma
flavonoids and it has been reported
to hybridize naturally
with P. calomelanos
1979). Most pteridologists currently consider this a morphological
ET AL.: PITYROGRAMMA
specialization within Pityrogramma,
although a strong
case can be made, based
upon its unique frond dissection and flangeless
this taxon under the name Trismeria.
The second anomaly discussed by Tryon (1962) is P. lehmannii (Hieron.)
Tryon, a rare species endemic to Colombia. It possesses a linear, pinnatisect
lamina with fully adnate pinnae that contain numerous veins arising directly
from the rachis and also has fronds spaced on the rhizome (rather than
multicipetally clustered). Its spores and sulcate stipes are, however, typical for
As with P. trifoliata, the farina of this species is not unusual for
being composed primarily
of a dihydrochalcone
that is one of the
eight principal flavonoids found in the genus (Wollenweber
Dietz, 1980). This
species is poorly known taxonomically and its disposition with regard
to the rest
of the genus must await further
In reviewing the taxonomic literature,
we were unable to find the existence of
another valid generic name for the P. triangularis complex. We therefore
reluctantly coin a new generic epithet, whose etymology may be explained by
the pentagonal (or
five-lined) architecture of fronds in this group.
Differt a Pityrogramma Link paleis rhizomatis distincte bicoloribus, ad
marginem pallidis, ad medium nigrescentibus; stipitibus teretibus; fasciculis
vascularibus stipitis singularibus;
laminis pentagonis, latitudine longitudinum
fere aequantibus, segmentis sessilibus usque adnatis;
sporis fulvis, tuberculatis,
sine porcis annularibus equatoris atrofuscis; chromosomatum
Rhizome slender, short, usually ascending;
fronds 7-40 cm long, clustered at
apex of rhizome; stipe usually longer than the lamina, brown to black, terete,
with a single vascular bundle; lamina deltate-pentagonal,
1-2-pinnate-pinnatifid with pinnatifid apex, about as long as wide or
occasionally somewhat longer
than wide, densely to sparsely
to farinose or viscid-glandular
adaxially; pinnae sessile to fully adnate,
the proximal basiscopic pinnules enlarged; venation free, dichotomously
branching; sporangia along veins (sometimes
surface), exindusiate, 64-spored;
concolorous, tan to brown,
lacking an equatorial flange, coarsely tuberculate with somewhat fused
tubercules; x = 30 (Alt &
Grant, 1960, among others).
TYPE: Pityrogramma triangularis (Kaulf.) Maxon
DISTRIBUTION: Western United States (Arizona, California, Nevada, New Mexico, Utah) and
adjacent Canada (British Columbia) and Mexico (Baja California Norte, Sonora); inhabiting rock
crevices. Plants are seasonal perennials
whose fronds curl during
times of drought.
The P. triangularis complex has been studied intensively in
portions of California,
beginning with the cytotaxonomic work of Alt & Grant
AMERICAN FERN JOURNAL:
VOLUME 80 NUMBER 1 (1990)
(1960). Various qualitative and quantitative
aspects of flavonoid biochemistry
have been elucidated in a lengthy series of reports
by Smith, Star,
and their collaborators
(see Wollenweber (1978) and Smith (1980) for reviews).
These studies suggested
the existence of a complex pattern
of autopolyploid and
allopolyploid evolution resulting in a confusing array of morphologically
cryptic taxa. The group has been circumscribed
variously as containing three
(Alt & Grant, 1960; Lellinger, 1985), two (Maxon, 1913; Smith, 1980), or one
1920) species, with various
taxa ascribed to P. triangularis. Even in the strict sense, Alt and Grant
distinguished two morphological
types and Smith (1980)
within P. triangularis,
The classification detailed here generally follows that proposed by Smith
(1980). We attempt to provide taxonomic recognition for the diploid entities
having some form of geographical, morphological, and biochemical integrity.
We have not recognized all of these taxa at the species level, because persistent
of widespread introgression
have yet to be
biosystematic studies. Morphological
among the taxa are too subtle to allow complete revision of the complex from
present data. We have excluded a single name in our transfer of taxa to
Pentagramma: Pityrogramma triangularis var. viridus Hoover. Smith et al.
(1971) have shown that this is a name of uncertain application, applied to a
number of different sterile hybrids of varying ploidy (and probable
We concur with Smith (1980) that this name should not continue to be used.
The following key will allow determination
of the majority
of plants in the
genus. Users should be aware
have been documented,
are not accounted for in the key.
KEY TO THE SPECIES
1. Rhizome apices farinose;
at least in young fronds;
fronds white-farinose adaxially and abaxially, appearing grayish adaxially
when fresh .................................... P. pallida
1. Rhizome apices and usually stipes glabrous
or somewhat glandular,
farinose; fronds yellow- or white-farinose abaxially, glabrous or with
scattered, clear, nonfarinose glands adaxially, appearing bright green or
sometimes yellowish green
adaxially when fresh. 2. P. triangularis
2. Fronds viscid adaxially; distal pinnae mostly entire; proximal basiscopic
lobes of basal pinnae entire to undulate or crenate ..... 2b. subsp. viscosa
or with scattered
glands adaxially, not
viscid; distal pinnae mostly regularly
lobed; proximal basiscopic lobes of
basal pinnae pinnatifid, often deeply so
3. Fronds with scattered, yellowish, capitate, nonfarinose glands
adaxially, white-farinose abaxially
............... 2d. subsp. maxonii
3. Fronds glabrous
adaxially, yellow- or white-farinose
light to bright
yellow ................ 2a. subsp. triangularis
4. Farina white ........................... 2c. subsp. semipallida
et stat. nov. Pityrogramma triangularis (Kaulf.) Maxon var. pallida Weath.,
Rhodora 22:119. 1920. Pityrogramma pallida (Weath.)
K. & V. Grant,
12: 168. 1960.-TYPE: U.S.A.: Madera County, California, hills about 3 mi above
Pollasky, 11 Apr 1906, Heller 8141 (holotype: GH!,
photo: MO!, isotypes: DS,
(1920), Alt & Grant
(1960), and Smith (1980) agreed
that this taxon
the most easily distinguishable
in the group, particularly
in the field.
In addition to the key characters,
the usually blackish, nonlustrous stipes of this
species are unique in the genus, as is the production of several C-methylated
flavanones in its farina
et al., 1987, and references
diploid species is endemic to the foothills of the Sierra Nevada in North-Central
counties). Alt & Grant
(1960) noted an apparent
between this species and P. triangularis
in Tuolumne County,
otherwise the species seem biologically distinct.
2. Pentagramma triangularis (Kaulf.)
Yatskievych, Windham, &
comb. nov. Gymnogramma triangularis Kaulf., Enum. Fil. 73. 1824.
Pityrogramma triangularis (Kaulf.) Maxon, Contr. U.S. Natl. Herb. 17:173.
1913.-TYPE: U.S.A.: California [near San Francisco; fide Alt & Grant, 1960],
1816 Chamisso s.n. (holotype:
2a. subsp. triangularis.
We presently restrict P. triangularis
to plants with yellow
farina and glabrous
adaxial frond surfaces
Norte). This subspecies comprises a complex of morphological,
cytological, and phytochemical variants, as documented by Alt &
and Smith (1980). At least some of these may deserve formal taxonomic
recognition, following more detailed studies. Wollenweber & Smith (1981)
noted that the holotype of P. triangularis
the chemotype producing
ceroptin, a novel flavonoid-like substance, as the major
constituent of its farina.
Plants with yellow farina from Arizona (Reeves, 1981), Nevada, and Utah (Alt &
1960) may represent
tetraploid hybrids between subsp. triangularis
subsp. maxonii (unpubl. data).
2b. subsp. viscosa (Nutt. ex D. Eaton)
Yatskievych, Windham, &
comb. et stat. nov. Gymnogramme
viscosa Nutt. ex D. Eaton, Ferns N. Amer.
2:16. 1879. Pityrogramma triangularis (Kaulf.)
Maxon var. viscosa (Nutt. ex D.
Weath., Rhodora 22:117. 1920. Pityrogramma
ex D. Eaton)
Maxon, Contr. U.S. Natl. Herb. 17:173. 1913.-TYPE: U.S.A., California, San
Diego, Nuttall s.n. (holotype:
This diploid is a largely coastal taxon, found in southern California and
adjacent Baja California Norte. Its major exudate constituent is
2',6'4-trihydroxy, 4'-methoxy, 3'-methyl dihydrochalcone (Wollenweber
1979). Alt &
(1960) reported introgression
between this taxon and subsp.
noting diploid and tetraploid plants of intermediate
some sites where these two co-occur.
Alt & Grant
also identified a single putative
tetraploid hybrid between subsp. viscosa and subsp. maxonii from San Diego
AMERICAN FERN JOURNAL:
VOLUME 80 NUMBER 1 (1990)
2c. subsp. semipallida (J. Howell) Yatskievych, Windham, & Wollenweber,
comb. et stat. nov. Pityrogramma
Maxon var. semipallida
W. Bot. 9:223.1962-TYPE: U.S.A.: California,
rocks in canyon of North
9 mi NE of Oroville,
20 Sep 1959, Howell 34696 (holotype:
isotypes: G, US).
This taxon, whose flavonoid exudate consists principally of kaemferol-3,
4'-dimethyl ether (Smith, 1980), remains heterogeneous as currently treated.
Plants from the foothills of the Sierra
are diploid. Smith
et al. (1971) documented a tetraploid race of P. triangularis of similar
morphology (including white farina), apparently restricted to Santa Barbara
County and the adjacent Channel Islands in southern California. The
relationship between those two variants has not been studied in detail.
2d. subsp. maxonii (Weath.) Yatskievych,
Wollenweber, comb. et
stat. nov. Pityrogramma triangularis (Kaulf.) Maxon var. maxonii Weath.,
Rhodora 22:119. 1920.-TYPE: U.S.A., Arizona [Pima County], Rincon
Mountains, head of Rincon Valley, under dripping
rocks, 3500 ft, 27 July 1909,
Blumer 3271 (holotype:
US; isotypes: ARIZ!, DS, GH,
This taxon has been treated as a variety of P. triangularis by all previous
Plants occur in central
and somewhat disjunctly
in southern California
and San Diego Counties)
Smith (1980) showed that the primary
of the farina of this taxon is
the flavonol galangin, which is rarely
observed in other diploid members
genus. However, he claimed that this taxon showed evidence of hybridization
with subsp. triangularis
with little or no reduction
hypothesized that introgression
also was occurring
between subsp. maxonii and
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and G. SCHILLING. 1987. Structure revision for two C-methyl
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and I. DE
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