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BFNA Title: Petalophyllaceae |
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XX. PETALOPHYLLACEAE Stotler
& Crand.-Stotl. Barbara J. Crandall-Stotler Plants thallose,
simple or once furcate, light green to light yellow green, growing solitary
or in small [large] patches. Thallus wings
flattened to erect, fan-shaped, multistratose at the base, becoming
unistratose at the margin, with [without] erect dorsal lamellae; midrib
fleshy, dorsally compressed (concave), with a ventral mycorrhizal
zone; central strand absent; ventral surface with 2 rows of small scales;
rhizoids hyaline. Asexual reproduction
by perennating apical tubers. Dioicous,
heterothallic [homothallic], gametangia dorsal on thallus midrib; antheridia
dispersed [clustered], subtended by lamellar extensions, or [interspersed
with small bracts]; archegonia clustered, mixed with paraphyses, surrounded
by a pseudoperianth. Sporophytes
enclosed in a thin shoot calyptra and enlarged pseudoperianth; capsules
spheroidal, nonvalvate, dehiscence irregular;
capsule walls 3--4-stratose, with secondary thickenings in all layers. Genera 2 (1 in the
flora): Known from North America, w Europe, n
Africa, India, New Zealand, and w Australia. Petalophyllaceae was segregated from the Fossombroniaceae
on the basis of the following characters that differentiate Petalophyllum (and Sewardiella) from Fossombronia: undissected, thallose
gametophyte; clustered archegonia, surrounded by a pseudoperianth; capsule
walls 3--4-stratose throughout; secondary cell wall thickenings in all
capsule wall layers. Molecular phylogenetic studies further support its
segregation from the Fossombroniaceae (B. J.
Crandall-Stotler et al. 2005). Selected References:
Crandall-Stotler, B. J., R. E. Stotler and C. H.
Ford. 2002. Contributions towards a monograph of Petalophyllum (Marchantiophyta). Novon 12:
334--337. Crandall-Stotler, B. J., L. L. Forrest and R. E. Stotler. 2005. Evolutionary trends in the simple thalloid
liverworts (Marchantiophyta, Jungermanniopsida
subclass Metzgeriidae). Taxon 54: 299--316. 1. PETALOPHYLLUM Nees & Gottsche ex Lehmann,
Nov. Stirp. Pugillus
8: 29. 1844 [Greek, petalos,
broad, and phyllo,
leaf] Plants large, to 11.2 mm x 9
mm. Wings with obliquely oriented,
dorsal lamellae; wing margin entire or highly erose, with or without marginal
cells distinct; cells thin-walled, without trigones; oil bodies small,
spheroidal, homogeneous, 40--75 per cell. Lamellae leaf-like, extending from the costa to near the wing
margin, mostly 1-stratose, multistratose at the base, with the margins
entire, plane, undulate, or sinuate. Heterothallic,
male plants smaller than female. Antheridia
arranged in 1--5 rows near the thallus apex, individually subtended by lobed
extensions of the lamellae, yellow at maturity, stalk 4-seriate. Gynoecia 1--3 per thallus; pseudoperianths cylindric to broadly companulate,
the outer surface with or without wing-like, lamellar outgrowths, the inner
surface smooth; the mouth erect to incurved or recurved, subentire, coarsely
toothed or highly lacerate, with or without 1-seriate cilia. Spores large, spheroidal, light to
dark reddish brown, areolate on both proximal and distal faces, with a
central, proximal depression. Species 5 (1 in the
flora): best known from seasonally dry habitats in North America, w Europe, n Africa, India, New Zealand, w Australia. 1. Petalophyllum americanum C. H. Ford & Crand.-Stotl., Novon 12: 335. 2002 E Plants 4--8 mm x 2.5--6.5 mm,
in small, scattered patches on exposed, sandy soil, often among grasses. Wings flattened to suberect, with the margins entire, plane to slightly undulate;
median cells elongate, 50--80 /um x 40--52 /um; marginal cells smaller,
quadrate or tangentially elongate, 36--40 /um x 34--44 /um; lamellae with the margins plane to slightly
undulate, never sinuate; ventral scales subulate, 120--160 /um x 45--60 /um,
2(--3) cells wide at the base, with 1--3 short marginal cilia, terminated by
slime papillae. Male plants 2.5--3.2
mm wide; thallus wings suberect; antheridia in 2--3 irregular rows. Gynoecia
1(--2) per thallus, with 5--9 archegonia per gynoecium; pseudoperianths
campanulate, 1.5--3.1 mm x 1.9--4.3 mm, with 1(--2)
lengthwise slits on the acroscopic side, laterally
confluent with the wing lamellae; outer surface with vertical wing-like
lamellae 2--5 cells high; the mouth erect to incurved, sinuate, subentire to
coarsely dentate, never ciliate. Sporophytes
1(--2) in each pseudoperianth. Capsules
dark brown to black, 1.4--2.3 mm; outer cells quadrate, with reddish
brown, nodular, I-type thickenings on all radial walls; inner cell layers
with reddish brown semiannular thickenings. Spores 48--60 /um. Elaters 240--300 x 12--16 /um,
occasionally branched, with 3--4(--5) reddish brown spiral thickening bands,
becoming 2-spiraled at the ends. Capsules mature Feb. to
March; found among grasses on sandy, seasonally dry soils of disturbed sites
such as pastures, cemeteries and parks, often associated with Fossombronia, Corsinia, and Riccia; North
American endemic of the Gulf Coastal Plain and Interior Highlands; low to
moderate elevations; Ark., La., Miss., Tex. A. W. Evans (1919)
first reported Petalophyllum
for North America, based on his study of two collections from Texas. These
initial specimens were referred to P. ralfsii, a well-known species of the British Isles
and Mediterranean region, an application that persisted in subsequent North
American treatments of the genus, including that of R. M. Schuster (1992). A
detailed morphological comparison of North American specimens with the type
and numerous collections of European P.
ralfsii by B. J. Crandall-Stotler et al.
(2002), however, provided convincing evidence that the North American plants
are a distinct species, which was named P.
americanum. Major distinguishing characters of this North American
endemic are as follows: (1) thalli typically smaller than those of P. ralfsii, (2)
wings and lamellar margins plane to slightly undulate, compared to sinuate in
P. ralfsii,
(3) pseudoperianth mouth subentire to coarsely toothed, compared to laciniate
with uniseriate cilia in P. ralfsii, (4) elaters 3--4(--5)-spiraled compared to
2--3-spiraled in P. ralfsii.
The thalli of P. americanum are
present only from January through March, forming subterranean apical tubers
soon after antheridial and sporophyte maturation.
Following tuber formation, the thallus dies, and the plant persists as either
spores or tubers in the soil bank. SELECTED REFERENCES Bloomquist, H. L. 1939. Notes on Southern Hepaticae.
Bryologist 42: 31--32. Crandall-Stotler, B. J., R. E. Stotler,
and C. H. Ford. 2002. Contributions toward a monograph of Petalophyllum (Marchantiophyta).
Novon 12: 334--337. Evans, A. W. 1919. Notes on
North American Hepaticae---VIII. Bryologist 22: 54--73. Kyzer,
J. W. and D. L. Marsh. 1999. Occurrences of Petalophyllum (Fossombroniaceae)
in the Interior Highlands of Arkansas. J. Arkansas Acad. Sci. 53: 145--146.
Schuster, R. M. 1992. The Hepaticae and Anthocerotae of North America, Vol.
V. Field Museum, Chicago. |
