A Reconsideration of the Genus Pityrogramma (Adiantaceae) in Western North America

Abstract

The silverback and goldback ferns of the genus Pityrogramma Link are striking, graceful plants of small to medium size, well known to fern fanciers for 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. Presl) Ching; see Pichi Sermolli, 1986) and the taxa were last revised taxonomically by Tryon (1962), who recognized 14 species.

Full text

American
Fern
Journal
80(1):
9-17 (1990)
A Reconsideration of the Genus Pityrogramma
(Adiantaceae) in Western North America
GEORGE YATSKIEVYCH
Missouri
Botanical
Garden,
P.O. Box 299, St. Louis,
MO
63166
MICHAEL
D. WINDHAM
Utah Museum
of Natural
History,
University
of Utah,
Salt Lake
City,
UT 84112
ECKHARD
WOLLENWEBER
Institut
fiir
Botanik der Technischen
Hochschule,
Schnittspahnstrasse
3,
D-6100
Darmstadt,
West
Germany
The silverback and goldback ferns of the genus Pityrogramma Link are
striking,
graceful plants of small to medium size, well known to fern fanciers
for
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.
Presl) Ching;
see Pichi Sermolli, 1986)
and the taxa were last revised taxonomically by Tryon
(1962),
who recognized 14
species.
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
(1960),
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 &
Grant
(1960).
At the generic level there has been growing
recognition
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 &
Tryon (1982)
suggested that the southwestern complex might be better classified in the tribe
Cheilantheae
rather
than the tribe
Taenitideae,
but postponed formal
taxonomic
segregation
from
Pityrogramma
until the group's
affinities became better known.
During
studies leading to treatments
for
the genus Pityrogramma
for
the Flora
of North America Project and the Ferns and Fern Allies of the Southwestern
United States (Windham
&
Yatskievych,
in prep.)
we also concluded that the P.
triangularis complex should be segregated
from Pityrogramma.
This paper is
intended to review the rationale for distinguishing these two morphologically

AMERICAN FERN JOURNAL:
VOLUME 80 NUMBER 1 (1990)
convergent groups and to supply the new nomenclatural combinations
necessary to accommodate
ongoing floristic
projects.
GENERIC
CONSIDERATIONS
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
sharply
bicolorous, with strongly
darkened central
stripes
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
deltate-pentagonal
in the western North American
complex (accounting
for the
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
recently, Kramer
(1987)
noted that members of the P. triangularis complex are unique in frequently
having catadromous venation (actually,
venation is catadromous above
the basal
pair
of pinnae, which are
basiscopically elaborated
and catadromous
with regard
to their pinna apex, but appear anadromous
with regard
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;
Tryon
&
Tryon,
1982). Typical Pityrogramma
spores possess an equatorial
flange
with 1-4 accessory, parallel ridges (Fig. 1). In addition, the spores are
bicolorous, with dark brown ridges over a tan matrix. Pityrogramma
trifoliata
(L.)
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
tuberculate
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
equatorial
flange)
more than they do those of the tribe Taenitideae (almost
all of
which have spores with an equatorial
flange).
Our
knowledge of the cytology of Pityrogramma
is somewhat ambiguous,
due
to the disproportionate
number of inexact counts in the literature. Walker
(1966)
counted five species, P. calomelanos (L.)
Link,
P. aff.
chrysophylla (Sw.) Link,
P.
ebenea (L.)
Proctor
(as P. tartarea
(Cav.)
Maxon),
P. sulphurea (Sw.) Maxon,
and
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
10

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
11

AMERICAN FERN JOURNAL:
VOLUME 80 NUMBER 1 (1990)
species from
Jamaica.
These data
suggest
that
Pityrogramma
sensu stricto
may
be
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
base number.
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
classification, because
all other members of the tribe Taenitideae (apparently
including Pityrogramma
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
the striking
farinas of the goldback
and
silverback
ferns have been studied in detail by a number
of workers
(see review
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
complex produced
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
the genus.
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
&
Tryon
(1982),
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
segregation
at the generic level.
Much research is still necessary to refine generic affinities within the
Adiantaceae
and even Pityrogramma
sensu stricto contains
further
problems.
As
detailed by Tryon (1962), two further anomalous
species have been classified in
the genus. The first,
Pityrogramma trifoliata
(L.)
R.
Tryon
(= Trismeria
trifoliata
(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
(L.)
Link (three
varieties)
and P.
ferruginea
(Kunze)
Maxon
(Tryon,
1962;
Gomez,
1979). Most pteridologists currently consider this a morphological
12

YATSKIEVYCH
ET AL.: PITYROGRAMMA
specialization within Pityrogramma,
although a strong
case can be made, based
upon its unique frond dissection and flangeless
spores, for
generic segregation
of
this taxon under the name Trismeria.
The second anomaly discussed by Tryon (1962) is P. lehmannii (Hieron.)
R.
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
Pityrogramma.
As with P. trifoliata, the farina of this species is not unusual for
Pityrogramma,
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
study.
TAXONOMIC
CONCLUSIONS
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.
Pentagramma
Yatskievych,
Windham,
&
Wollenweber,
gen. nov.
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
numero basali
x=30.
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
farinose
abaxially,
glabrous
to farinose or viscid-glandular
adaxially; pinnae sessile to fully adnate,
the proximal basiscopic pinnules enlarged; venation free, dichotomously
branching; sporangia along veins (sometimes
nearly obscuring
the abaxial
frond
surface), exindusiate, 64-spored;
spores tetrahedral,
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.
DISCUSSION:
The P. triangularis complex has been studied intensively in
portions of California,
beginning with the cytotaxonomic work of Alt & Grant
13

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,
Wollenweber,
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
(Mickel, 1979;
Tryon, 1962;
Weatherby,
1920) species, with various
infraspecific
taxa ascribed to P. triangularis. Even in the strict sense, Alt and Grant
(1960)
distinguished two morphological
types and Smith (1980)
four
biochemical types
within P. triangularis,
which remain
uncorrelated.
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
reports
of widespread introgression
in areas
of geographic
contact
have yet to be
evaluated through
further
biosystematic studies. Morphological
discontinuities
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
parentage).
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
that
several
hybrids
have been documented,
which
are not accounted for in the key.
KEY TO THE SPECIES
OF
PENTAGRAMMA
1. Rhizome apices farinose;
stipes farinose
throughout,
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,
but not
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
subsp. (2)
2. Fronds viscid adaxially; distal pinnae mostly entire; proximal basiscopic
lobes of basal pinnae entire to undulate or crenate ..... 2b. subsp. viscosa
2. Fronds
glabrous
or with scattered
yellowish, capitate
glands adaxially, not
viscid; distal pinnae mostly regularly
lobed; proximal basiscopic lobes of
basal pinnae pinnatifid, often deeply so
......................... (3)
3. Fronds with scattered, yellowish, capitate, nonfarinose glands
adaxially, white-farinose abaxially
............... 2d. subsp. maxonii
3. Fronds glabrous
adaxially, yellow- or white-farinose
abaxially
...... (4)
4. Farina
light to bright
yellow ................ 2a. subsp. triangularis
4. Farina white ........................... 2c. subsp. semipallida
14

YATSKIEVYCH
ET
AL.:
PITYROGRAMMA
1. Pentagramma
pallida (Weath.)
Yatskievych,
Windam,
&
Wollenweber,
comb.
et stat. nov. Pityrogramma triangularis (Kaulf.) Maxon var. pallida Weath.,
Rhodora 22:119. 1920. Pityrogramma pallida (Weath.)
K. & V. Grant,
Brittonia
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,
MO!).
Weatherby
(1920), Alt & Grant
(1960), and Smith (1980) agreed
that this taxon
was among
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
(Markham
et al., 1987, and references
cited therein).
This
diploid species is endemic to the foothills of the Sierra Nevada in North-Central
California
(Butte
to Kern
counties). Alt & Grant
(1960) noted an apparent
case of
hybridization
between this species and P. triangularis
in Tuolumne County,
but
otherwise the species seem biologically distinct.
2. Pentagramma triangularis (Kaulf.)
Yatskievych, Windham, &
Wollenweber,
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:
B!).
2a. subsp. triangularis.
We presently restrict P. triangularis
subsp. triangularis
to plants with yellow
farina and glabrous
adaxial frond surfaces
occurring
throughout
a large
region in
westernmost North
America
(British
Columbia,
Washington,
Oregon,
California,
Baja
California
Norte). This subspecies comprises a complex of morphological,
cytological, and phytochemical variants, as documented by Alt &
Grant
(1960)
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
represents
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 &
Grant,
1960) may represent
tetraploid hybrids between subsp. triangularis
and
subsp. maxonii (unpubl. data).
2b. subsp. viscosa (Nutt. ex D. Eaton)
Yatskievych, Windham, &
Wollenweber,
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.
Eaton)
Weath., Rhodora 22:117. 1920. Pityrogramma
viscosa (Nutt.
ex D. Eaton)
Maxon, Contr. U.S. Natl. Herb. 17:173. 1913.-TYPE: U.S.A., California, San
Diego, Nuttall s.n. (holotype:
PH!).
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
et al.,
1979). Alt &
Grant
(1960) reported introgression
between this taxon and subsp.
triangularis,
noting diploid and tetraploid plants of intermediate
morphology
at
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
County.
15

AMERICAN FERN JOURNAL:
VOLUME 80 NUMBER 1 (1990)
2c. subsp. semipallida (J. Howell) Yatskievych, Windham, & Wollenweber,
comb. et stat. nov. Pityrogramma
triangularis (Kaulf.)
Maxon var. semipallida
J.
Howell, Leafl.
W. Bot. 9:223.1962-TYPE: U.S.A.: California,
Butte
County,
on
metamorphic
rocks in canyon of North
Fork
Feather
River,
9 mi NE of Oroville,
20 Sep 1959, Howell 34696 (holotype:
CAS;
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
Nevada
in Butte
County
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,
Windham, &
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,
MO!).
This taxon has been treated as a variety of P. triangularis by all previous
workers.
Plants occur in central
and southern
Arizona
and somewhat disjunctly
in southern California
(Riverside
and San Diego Counties)
and adjacent
Mexico
(Baja
California
Norte, Sonora).
Smith (1980) showed that the primary
constitutent
of the farina of this taxon is
the flavonol galangin, which is rarely
observed in other diploid members
of the
genus. However, he claimed that this taxon showed evidence of hybridization
with subsp. triangularis
with little or no reduction
in fertility.
Alt &
Grant
(1960)
hypothesized that introgression
also was occurring
between subsp. maxonii and
subsp. viscosa.
LITERATURE CITED
ALT, K. S. and V. GRANT. 1960. Cytotaxonomic observations on the goldback fern. Brittonia
12:153-170.
G6MEZ, L. D. 1979. Contribuciones a la pteridologia Costarricense XII. Novitates. Brenesia
16:95-100.
KRAMER, K. U. 1987. A brief survey of dromy in fern leaves, with an expanded terminology. Bot.
Helv. 97:219-228.
LELLINGER,
D. B. 1985. A field manual of the ferns & fern-allies of the United States & Canada.
Smithsonian Institution Press, Washington, DC.
LOVE,
A., D. LOVE,
and R. E. G. PICHI SERMOLLI.
1977. Cytotaxonomical atlas of the Pteridophyta.
J. Cramer, Vaduz, Liechtenstein.
MARKHAM,
K. R., E. WOLLENWEBER,
and G. SCHILLING. 1987. Structure revision for two C-methyl
flavanones from Pityrogramma pallida. J. P1. Physiol. 131:45-48.
MAXON,
W. R. 1913. Studies of tropical American ferns-No. 4. Contr. U.S. Natl. Herb. 17:133-179 +
10 pl.
MICKEL,
J. T. 1979. How to know the ferns and fern allies. Wm. C. Brown Co., Dubuque, IA.
MUNZ, P. A. and D. D. KECK.
1968. A California flora, with supplement by P. A. Munz. Univ. of
California Press, Berkeley, CA.
PIcm SERMOLLI,
R. E. G. 1986. Report of the subcommittee for family names of Pteridophyta. Taxon
35:686-691.
16

YATSKIEVYCH ET AL.: PITYROGRAMMA
REEVES,
T. 1981. Notes on North American lower plants-II. Amer. Fern J. 71:62-64.
SMITH,
D. M. 1980. Flavonoid analysis of the Pityrogramma triangularis complex. Bull. Torrey Bot.
Club 107:134-145.
SMITH, D. M., S. P. CRAIG, and J. SANTAROSA.
1971. Cytological and chemical variation in
Pityrogramma triangularis. Amer. J. Bot. 58:292-299.
TRYON,
A. F., H. P. BAUTISTA,
and I. DE
SILVA
ARAOJO.
1975. Chromosome studies of Brazilian ferns.
Acta Amazonica 5:35-43.
TRYON,
R. 1962. Taxonomic fern notes. II. Pityrogramma (including Trismeria) and Anogramma.
Contr. Gray Herb. 189:52-76.
TRYON,
R. M. and A. F. TRYON. 1982. Ferns and allied plants, with special reference to tropical
America. Springer-Verlag, New York.
WAGNER,
W. H. 1963. A biosystematic survey of United States ferns-preliminary abstract. Amer.
Fern J. 53:1-16.
WALKER,
T. G. 1966. A cytotaxonomic survey of the pteridophytes of Jamaica. Trans. Roy. Soc.
Edinburgh 66:169-237 + 5 pl.
WEATHERBY,
C. A. 1920. Varieties of Pityrogramma triangularis. Rhodora 22:113-120.
WOLLENWEBER,
E. 1978. The distribution and chemical constituents of the farinose exudates in
gymnogrammoid ferns. Amer. Fern J. 68:13-28.
WOLLENWEBER,
E. and V. H. DIETZ. 1980. Flavonoid patterns in the farina of goldback and silverback
ferns. Biochem. Syst. Ecol. 8:21-33.
WOLLENWEBER, E., V. H. DIETZ,
G. SCHILLING,
J. FAVRE-BONVIN,
and D. M. SMITH.
1985. Flavonoids
from chemotypes of the goldback fern, Pityrogramma triangularis. Phytochemistry
24:965-971.
WOLLENWEBER, E., V. H. DIETZ, D. M. SMITH, and D. S. SEIGLER.
1979. A novel C-methylated
dihydrochalcone from Pityrogramma triangularis var. viscosa. Z. Naturf. 34c:876-877.
WOLLENWEBER,
E. and D. M. SMITH. 1981. The chemoidentity of the holotype of Pityrogramma
triangularis. Amer. Fern J. 71:120.
17