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BFNA Title: Acrobolbus |
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XX. ACROBOLBACEAE E A. Hodgson Laura Briscoe and John J. Engel Plants prostrate to erect. Branches originating from the axils
of lateral leaves [occasionally from axils of underleaves]; sometimes with
flagellae. Rhizoids hyaline, tending to
be in fascicles from ventral base of leaves, sometimes scattered. Leaves
alternate, succubous, concave to somewhat convex, [unlobed] bilobed [or
rarely 2--4(--5)-lobed], margins entire or bearing rhizoids [or dentate to
dentate-ciliate]. Underleaves absent or vestigial [present and well developed]. Asexual reproduction lacking or by caducous leaves. Gynoecium
terminal on leafy branches [or on abbreviated intercalary branches]. Subfloral inovations
common. Perianth rudimentary
or absent. Marsupium present, pendent. Genera 6 (1 in
flora): North America, Central America, South America, Europe, Asia, Africa,
Atlantic Islands, Pacific Islands, Australia. Acrobolbaceae is a small family, circumscribed in four subfamilies, with
most of the diversity in the southern hemisphere. Acrobolbus, the sole North American member, belongs in the
subfamily Acrobolboideae R.M. Schuster ex Briscoe.
Plants of Acrobolboideae can grow terrestrially, as
in A. ciliatus,
or as epiphytes, but require very moist growing conditions. They often have a
distinctive opaque quality in their leaves and, when fertile, develop large,
hairy marsupia. SELECTED REFERENCES:
Schuster, R. M. 1980. Acrobolbus. In: The Hepaticae and Anthocerotae
of North America east of the hundredth meridian. New York. Vol. 4, pp.
539--554. Schuster, R. M. 2001. Revisionary studies on austral Acrobolbaceae, I. J. Hattori Bot. Lab. 90: 97--116. 1.
ACROBOLBUS Nees in
C. M. Gottsche, J. B. W. Lindenberg
& C. G. D. Nees, Syn. Hep. 5. 1844. [Greek: akros, at the tip, end,
and bolbos, bulb, alluding to the
apical marsupium] Plants
pure green to gray-, yellowish, whitish, or faintly bluish green to
brownish. Branching in
species that lack basal stolons sparing, the branches lateral-intercalary,
[other species often with a system of basal stolons from which arise erect,
leafy shoots that are mostly lateral-intercalary but at times
ventral-intercalary in origin, the leafy branches also originating from
sectors of the erect leafy shoots]; stoloniform axes absent, or (often)
abundant, basal, all intercalary and often originating from basal sector of
erect leafy shoots. Stems with cortical cells about equal
in diameter to the medullary cells or smaller, the cortical cells thin-walled
or slightly to
strongly thick-walled and [in some species in 1--3(--4) layers]; medullary
cells thin- to firm-walled. Rhizoids
sometimes from margins of leaves, [or on
stoloniform axes]. Leaves with insertion distinctly
succubous throughout, [or succubous in dorsal half and subtransverse
in ventral half]; the apex undivided to (often) retuse or bilobed to 0.3--0.6
the leaf length, the lobes frequently asymmetric and then with the dorsal
lobe always smaller, the lobes acute [to acuminate or at times piliferous],
entire, the lobes and lamina margins sometimes adorned with marginal rhizoids
[or variously toothed]. Androecia
lacking [terminal but becoming intercalary on leading shoots and then usually
subfoliose, or on short lateral- or
ventral-intercalary branches from lower leafless sector of shoot and then
spicate; antheridia 1--3 to 5--10 per
bract, the stalk long, to 29 cells long, 2--3-seriate]. Gynoecia
(only juvenile known), terminal
on leading shoots with a subfloral
innovation when unfertilized [ or on short branches originating
from basal stoloniform axes or from microphyllous
sector of erect leafy shoots], bracts
leaf-like, the outermost larger than leaves. Marsupium not seen [of Tylimanthus
type, cylindrical or conical, the surface
smooth or sparsely covered with rhizoids or with hyaline, stiff, unicellular
hairs]. [Sporophyte with long
seta, capsule ellipsoidal to long cylindrical with acute apex, the valves
straight, not twisted, the wall 2--3 or more often 4--9-stratose, outer walls
with nodular thickenings]. Species 40 (1 in
the flora): North America, West Indies, Central America, South America,
Europe, Asia, Africa, Atlantic Islands (including Macaronesia),
Pacific Islands (including Hawaii and New Zealand), Australia. SELECTED REFERENCES:
Schuster, R. M. 1980. Acrobolbus. In: The Hepaticae and Anthocerotae
of North America east of the hundredth meridian. New York. Vol. 4, pp.
539--554. 1.
Acrobolbus ciliatus (Mitten)
Schiffner in H.G.A. Engler & K. Prantl, Nat. Pflanzenfam.1 (3): 86. 1893 Gymnanthe ciliata
Mitten, J. Proc. Linn. Soc., Bot. 5 (18): 100. 1861 (1860); Acrobolbus rhizophyllus Sharp;
Acrobolbus (Lophocoleopsis)
titibuensis (S. Hattori) S. Hattori; Leiocolea titibuensis S. Hattori; Lophozia curiossima Horikawa Plants flexuous, prostrate, loosely creeping, opaque,
greyish green to whitish yellow. the shoots
10--25(--35) x 1.5--2.2 mm. Stems slender, the cortical cells in
surface view striate-papillose. Rhizoids
often exceeding length of leaf. Lateral
leaves strongly succubously inserted, plane to
convex, subsymmetrical, ovate to ovate-quadrate to
subquadrate-orbicular, often appearing subcuneate
in situ, 2-lobed to 0.3--0.45, sporadic leaves exceptionally 2-lobed; lobes
about equal in size, or commonly the ventral larger, the margins with several
to many rhizoids developing with age (leaves towards shoot apices devoid of
rhizoids), the rhizoids glistening, the lobe apices bluntly rounded or
terminating in a single, often sharp, cell or in a rhizoid; sinus acutely
angular to rounded at base; lamina margins edentate, armed with rhizoids
similar to the lobes, the dorsal margin nearly straight to arched, the
ventral margin typically more strongly arched than the dorsal; leaf cells
with thin walls, trigones medium and straight-sided to large with sides slightly
bulging; the median lamina cells (28--)32--38 x 25--32 \um
in leaf middle, 32--40 x 24--28 \um
at base; surface distinctly
papillose. Oil bodies nearly occluding the cell lumen, large for cell size,
somewhat opaque and greyish, (3--4)5--10(--12), finely granular, subspherical to ovoid to ellipsoid, 6 x 9 to 10 x 15 \um, or smaller in cells with 8 or more oil-bodies. Underleaves
lacking, except at shoot apices, 1--2 cells wide at base, 2--3 cells
long, bearing several slime papillae. Androecia lacking in flora area. Sporophyte
unknown. On damp to moist,
usually shaded noncalcareous rocks, in areas with
high atmospheric moisture or spray, such as near waterfalls or cascades;
restricted to elevations around 600 m; Alaska (Aleutian Islands), Ga., N.C.,
S.C., Tenn.; Asia (Japan, Sikkim-Himalaya). The only species of this family in
North America, Acrobolbus ciliatus is
locally rare and potentially threatened due to limited suitable habitat. It often occurs in only small quantity, and in admixture with
other bryophytes. It is an oceanic
species restricted to widely disjunct areas, the stations rare and local.
Regionally, it is found in small areas of the southern terminus of the
Appalachians, ranging from the upper edge of the Southern Escarpment into the
Smoky Mountains. Appalachian populations are
assumed to be sterile, with only immature female plants observed. Male plants
of the species appear to be restricted to Himalayan and Japanese populations.
The most striking feature of this species are the long
rhizoids borne on leaf margins. The oil body information is from R. M.
Schuster (1980). |
