Species Profiles

Phaeoceros

Phaeoceros carolinianus

Phaeoceros evanidus

Phaeoceros inflatus

Phaeoceros engelii

Introduction

The genus Phaeoceros is defined by the following characteristics combined: a solid thallus without any cavities; jacket cells of the antheridia arranged in an irregular pattern; the spores are bright yellow and possess a collar or cingulum around the circumference of the distal face.

Phaeoceros is probably the most speciose genus within the Austrtalian hornworts, however many species are still waiting to be described.

A recent publication (Cargill & Fuhrer, 2008) has described in detail, four Australian species. A pdf of the entire paper is attached below.

These descriptions will be repeated here but will also include many more images and line drawings that were not included in the publication.

Genus description

Phaeoceros Prosk., Bull. Torrey Bot. Club 78(4): 346 (1951)
Etymology: from the Greek phaeo- (dark) and ceros (a horn), in reference to the dark colouring and shape of the mature sporophyte.

Type: Phaeoceros laevis (L.) Prosk.

A widely occurring genus in both the Northern and Southern hemispheres Phaeoceros consists of c. 40 taxa, of which Phaeoceros carolinianus and P. laevis are the most widespread species world-wide (H�ssel de Men�ndez, 1987 Schuster 1992). Distinguishing characters for the genus in Australia include smooth solid thallus, yellow spores, irregularly arranged jacket cells of the antheridia, and possession of tubers in some species.

Species Descriptions

Phaeoceros carolinianus

NOMENCLATURE

Phaeoceros carolinianus (Michx.) Prosk. Bull. Torrey Bot. Club. 78: 347. 1951.
Basionym: Anthoceros carolinianus Michx. Flora Boreali-Americana 2: 280. 1803.
Type: USA. Carolina inferiori, herb. Camus, herb. Richard (holotype in PC)
Synonyms: Anthoceros australiae Beauverd ex Stephani Spec. Hepat. 6: 571 (1924) syn. nov. Type: Australia, New South Wales, F. v. Mueller (as A. crispus) (lectotype G!).
Anthoceros brotheri Stephani Hedwigia 32: 141 (1893) syn. nov. Type: Australia, Queensland, Brotherus 859 (lectotype in G!).
Anthoceros communis Stephani Bull. Herb. Boissier 5: 86 (1897). Type: Japan, Akita, Faurie 1484 (lectotype in G!) NSW 261411.
Anthoceros multicapsulus Stephani, Spec. Hepat. 5: 991 (1916) syn.nov. Type: Lord Howe Island. (lectotype in G!).

DESCRIPTION

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Thallus transparent yellow green to dark green (RHS Colour chart 135D; 137B,C & D, 144B) growing on soil or rock. Plants small to medium in size, up to 20mm in length and 15mm in width, forming fans, rosettes, patches or mats, adhering to bare soil or rock. Furcate to irregularly branched, frequently with ventral unstalked tubers becoming broad and flat, full of starch granules. Thallus solid, 8 – 12 cells thick in transverse section, varying from biconvex to plano-concave to concave-convex. Dorsal epidermal cells quadrate to hexagonal, 17 – 83 �m x 17 – 48 �m. Internal cells 26 – 82 �m x 26 – 70 �m. Ventral clefts observable sometimes and flanked by two cells. Nostoc colonies scattered through ventral half of thallus, appearing as dark dots. Rhizoids ventral, hyaline or pale brown.

Monoicous, androecium with 2 – 5 antheridia per cavity, jacket cells irregularly arranged, 256 x 133 �m, stalk up to 38.4 �m long. Involucre erect, conical-cylindrical, up to 6mm long, contracted at the mouth, 5-7 cells thick in transverse section. Sporophyte capsule up to 80mm long, exserted, opening by two valves becoming twisted with drying, with well-developed columella, becoming yellow and then dark brown with age from the apex down. Assimilative layer 4-5 cells thick and sporogenous layer 2 rows of spores. Epidermal cells of capsule elongated rectangular, 99 – 227 �m x 16 – 22.5 �m, walls becoming thickened with maturity, stomata present in the capsule wall. Spores bright yellow, rounded-tetrahedral equatorial diameter 36 – 43 �m. Distal face covered with numerous spines, proximal face finely rugose with button-shaped verrucae confined to the centre of each triradiate face. Proximal face with a distinct triradiate mark, covered in a sculpturing of small bacillar and button-like papillae along its length. Pseudoelaters thin walled, up to 5-cells in length, frequently branched, 43 – 199 �m long and 9.5 – 22 �m wide, pale brown.

ETYMOLOGY

“carolinianus” refers to the location of the type collection which was originally collected in North (or ?South) Carolina, USA.

DISTRIBUTION AND ECOLOGY

A ubiquitous species across Australia, it is typically found growing on bare soil, on and beside bush tracks, roadside banks and banks of waterways.

AFFINITIES AND DIFFERENTIATION

P. carolinianus is closely related to P. laevis with many Australian collections identified as P. laevis, but sexual condition and spore proximal patterns distinguish these two species. P. carolinianus is monoicous and proximal verrucae numbers are low and are confined to the central section of each triradiate face. The type spores of P. laevis have verrucae covering each of the triradiate faces and it is dioicous (Proskauer, 1951 H�ssel de Men�ndez, 1987). Phaeoceros laevis has not been confirmed to occur in Australia, and is probably confined to the northern hemisphere.

Phaeoceros evanidus

NOMENCLATURE

Phaeoceros evanidus (Stephani) Cargill & Fuhrer comb. nov.

Basionym: Anthoceros evanidus Stephani, Spec. Hepat. 5: 990 (1916).

Type: Australia, Port Denison, W.W. Birch (lectotype in G!).


DESCRIPTION

Thallus pale transparent yellow-green to green (RHS Colour Chart 143C & 145B), delicate, growing in rosettes on bare moist soil patches. Plants small up to 15mm long and 2.4 - 15 mm wide, from single lingulate thallus to + fan-shaped branched thallus with overlapping lobes originating from a persistent narrow, strap posteriorly, furcately branched. Margins irregularly crenulate to + entire, sometimes lateral margins curving upwards becoming canaliculate. Thallus solid, but some plants occasionally with large inflated epidermal cells giving the plant a “quilted” appearance typically seen in members of the Anthocerotaceae s.str. Thallus concave-convex to plano-convex in transverse section, 7 – 11 cells thick. Dorsal epidermal cells quadrate to hexagonal, 28 – 92 �m x 19 – 53.3 �m. Cells with single chloroplast and pyrenoid. Some populations with dorsal stalked obpyriform to obovoid-shaped propagules (583 – 1,000 x 473 – 500 �m). Surface of propagules crenulate due to bulging epidermal cells. Stalk up to 1,000 �m long and 500 �m wide, composed of rectangular cells with single orange chromoplast. Plants sometimes with ventral unstalked tubers. Ventral clefts flanked by two cells at apical notch. Nostoc colonies scattered through thallus appearing as dark dots. Rhizoids hyaline along ventral surface.

Monoicous, androecia scattered over dorsal surface, 1 - 4 antheridia per cavity, spherical yellow-orange, on short stalks, 115 – 132.5 x 82.5 – 100 �m, jacket cells irregularly arranged. Involucre erect and cylindrical, contracted at the mouth, 1.2 - 2.8 mm long, 4 – 10 cells thick. Capsules erect, 5 – 12 mm long, exserted, splitting by two valves, assimilative layer 4 – 7 cells thick in transverse section, sporogenous layer 2 cells thick, with well-developed columella. Epidermal cells of capsule elongate rectangular (66 – 143 �m x 8.5 – 19.2 �m) punctuated with stomata (33 x 21 �m). Spores bright yellow, rounded-tetrahedral, with smooth border, equatorial diameter from 32 - 49 �m. Distal surface with numerous coarse, wart-like protuberances, frequently coalescing in the centre of the face, with smaller scattered verrucae in between larger protuberances, equatorial girdle smooth. Proximal surface with distinct triradiate mark covered in small spherical to baculate papillae on either side of a narrow, smooth dehiscence line. The three triradiate faces of the proximal surface covered with distinct button-like verrucae. A distinct shallowly papillate margo encircles the entire proximal face. Pseudoelaters 1 – 3 cells, 36 - 164 �m x 9.5 - 33 �m, pale brown, thin-walled, occasionally branched.

ETYMOLOGY

“evanidus” in Latin means vanishing. Stephani was probably referring to the ephemeral nature of this species.

DISTRIBUTION AND ECOLOGY

This species is confined to the tropical north-eastern region of Australia from the Atherton Tablelands of Far North Queensland to northern New South Wales.

AFFINITIES AND DIFFERENTIATION

Possibly overlooked because of small size of plants, it is distinguished from both P. carolinianus and P. inflatus by its distinct spore patterning. The spore distal face of the former species is covered in spine like protuberances, while that of the latter species displays fewer less coarse protuberances. Both species also lack the number of distinct button-like verrucae covering each of the triradiate faces. The proximal micro-ornamentation between verrucae is lacking in P. evanidus while it is composed of interweaved vermiculae for both P. carolinianus and P. inflatus. It is also distinguished from P. inflatus by its monoicous sexual condition.

Phaeoceros inflatus

NOMENCLATURE

Basionym: Anthoceros inflatus Stephani, Spec. Hepat. 5: 990. 1916.

Type: Australia, New South Wales, Uralba, W.W.Watts 391 (lectotype in G!, isolectotype in NSW!).

DESCRIPTION


Thallus bright green to yellow green to olive green (RHS Colour Chart: males 144A & B; females 143B), becoming brown when dried, growing on soil or rocks in mats or rosettes. Female plants small to medium in size, up to 20 mm in length and 5 mm in width, irregularly branched, apices of branches spathulate. Thallus solid, 8-9 cells thick, usually concave-convex, fleshy. Margins of plants entire, undulate or irregularly crenulate. Dorsal epidermal cells rectangular to hexagonal, 28 – 79 �m x 20 – 56 �m. Plants frequently with ventral unstalked tubers. Ventral clefts not observed. Nostoc colonies scattered through the ventral portion of thallus as dark dots. Rhizoids ventral and hyaline or pale brown.


Dioicous, male plants smaller, up to 10 mm long and 2 mm wide. Androecium with (1- )2 - 3 antheridia per cavity, ovoid to spherical, white to bright yellow, sunken into thallus, 163-250 x 133-150 �m on short stalks, cells of jacket irregularly arranged. Involucres erect cylindrical, up to 4 mm long. Capsules up to 40 mm long, one per involucre, splitting on either one or two sides by way of two valves, frequently remaining attached at apex, stomata scattered throughout epidermal layer, 61 – 77 �m x 41 – 51 �m, assimilative layer 5-7 cells thick in transverse section, sporogenous layer 1 - 2 tetrad layers thick, with well-developed columella. Epidermal cells of capsule rectangular to hexagonal and elongate 59 - 187.5 �m x 15 – 30 �m. Spores yellow to yellow-grey, 37.5 – 56.5 �m in diameter, rounded-tetrahedral. Distal surface with irregularly scattered, coarse protuberances, variable in shape crowned with one to several blunt triangular-shaped, wart-like or tuberculate papillae, never spine-like, intervening surface wrinkled, finely papillate or nearly smooth. Proximal surface with distinct, broad triradiate mark, entire face surrounded by a distinct cingulum. Triangular faces, flat or concave, with fine interwoven vermiculate-like patterning on surface, verrucae confined to central section of each face and may be distinct or indistinct. Pseudoelaters pale brown to dark brown at maturity, transparent, thin-walled and 1-4 celled, (41-) 46 – 297 �m in length and 7.5 – 28 (-38.4) �m in width, linear or branched.

ETYMOLOGY

The species epithet “inflatus” arises from Stephani’s observation of an inflated assimilative layer within the capsule resulting in a bulging involucre (see Stephani’s Icones Hepaticarum).

DISTRIBUTION AND ECOLOGY

A relatively common species among the Australian anthocerotes, extending down the eastern area of Australia from Queensland down to Victoria. Typically found growing on moist soil of banks and pathways often in shaded habitats.

AFFINITIES AND DIFFERENTIATION

Stephani described this species from a specimen sent to him by Rev. W. W. Watts from the Richmond River at Uralba, NSW (Stephani 1916). His description of this taxon is somewhat confusing as he has described the thallus “cavernosa” which is typical of Anthoceros s.s. yet, he is clear that the spores are pale yellow and minutely papillate. Examination of the type specimen confirms its placement within the genus Phaeoceros with possession typically of a solid thallus, irregularly arranged jacket cells of the antheridia and yellow spores. It differs from both P. carolinianus and P. evanidus in its dioicous sexual condition and irregular coarse protuberances topped by smaller irregular shaped papillae observed on the distal face of the spores.

Phaeoceros engelii

NOMENCLATURE

TYPE: Australia. Victoria. Lower Glenelg National Park. Kentbruck Rd bridge over Moleside Crk. 11th Oct. 2006. Cargill & Fuhrer 1016 (Holotype CANB)
Latin diagnosis: Ab omnibus aliis speciebus Phaeoceratis propagulis numerosis habens praeter margines thalli, coloniis nostocinis ventralibus tumescentibus, et propriis eminentia trabeculatis in pagina distali sporarum, differt.

DESCRIPTION

Thallus yellow green (RHS Colour Chart 146A), but appearing dark green at habitat due to deep shade and becoming black-green when dried, growing on soil or rocks in mats close to edge of creek or on rocks in creek or on banks of creek. Female plants up to 60 mm long and up to 11 mm wide, irregularly furcate branching, frequently with young lateral branches forming on mature thallus, lobes lingulate at apices. Thallus solid, 8-13 cells thick, plano-convex to concave-convex in transverse section, fleshy. Margins of thallus irregularly crenulate, with some populations possessing margins fringed with deciduous propagules. Dorsal epidermal cells quadrate to hexagonal, 25 – 57.5 �m x 22.5 – 37.5 �m. Thickening of ventral apices observed in plants not unlike the ventral unstalked tubers typically seen in this genus. No ventral clefts observed. Nostoc colonies scattered through thallus becoming spherical and bulging significantly from ventral surface with maturity. Rhizoids ventral and pale brown.

Dioicous, male plants smaller, up to 21 mm long and 4 mm wide. Androecium with 2 antheridia per cavity, ovoid, pale yellow, sunken into thallus, 175 – 325 x 150 – 240 �m, on short stalks, jacket cells irregularly arranged. Involucres erect, cylindrical, flaring at base up to 5 mm long, 5-8 cells wide in transverse section. Capsules up to 30 mm long, one per involucre, exserted, becoming blackish brown at tips with maturation of spores, opening by two valves, 6-8 cells thick in transverse section, stomata scattered throughout epidermal layer, 72.5 – 90 �m x 42.5 – 60 �m. Epidermal cells of capsule rectangular to hexagonal and elongate 82.5 - 170 �m x 12.5 – 27.5 �m. Spores yellow, 38 – 56.3�m in diameter, rounded-tetrahedral. Distal surface covered in short irregular trabeculate protuberances frequently coalescing to form irregular lamellae. Proximal surface covered in numerous irregular shaped verrucae. Pseudoelaters pale brown at maturity, transparent, thin-walled and 1-4 celled, linear or branched, 67-223 �m in length and 15-23 �m in width.

engelii.gifengelii2.gifengelii3.gifengelii4.gif

ETYMOLOGY

Named for Dr John Engel to commemorate his 40 years in hepaticology.

DISTRIBUTION AND ECOLOGY

This species is known only from one location beside and within a creek in the Lower Glenelg National Park. Its habitat preference is very similar to that of most Megaceros populations in relatively shady conditions near running water. In fact when first collecting this hornwort we had thought that it was indeed a Megaceros. Subsequent maturation of the sporophytes and examination of the spores placed it squarely in the genus Phaeoceros.

AFFINITIES AND DIFFERENTIATION

Collections made in later years revealed plants with numerous deciduous propagules growing almost like a fringe around the margins of the thallus. They are also found growing in patches on the dorsal and ventral surfaces of the thallus. Not infrequently, it would appear that some propagules remained attached to the parent thallus and grow to produce secondary branches. Similar structures were also observed and described by Howe for the species Anthoceros vegetans M. Howe (Howe, 1934) and by Stephani for the Chilean species P. propaguliferus (Steph.) Prosk. (Stephani, 1917) Also peculiar to this species is the morphology of the mature Nostoc colonies which bulge out as a relatively large hemispherical growth from the ventral surface of the thallus, unlike the typical colonies which remain small and well embedded in the ventral portion of the thallus. This phenomenon has not typically been observed in other Australian species of Phaeoceros. The sexual condition and spore distal pattern distinguish this species from both P. carolinianus and P. evanidus, both of which are monoicous, while P. engelii is dioicous. Also the more robust habit of the populations of P. engelii separate it immediately from the more diminutive P. evanidus.
It differs from P. inflatus in its possession of numerous propagules but where these are not apparent, differs significantly in the spore distal patterns. The spores of P. inflatus while also displaying protuberances from the distal face, differ in their micro-morphology. P. engelii displays trabeculate protuberances, while P. inflatus displays typically fewer, coarser protuberances which are often crowned by another layer of spine-like or wart-like papillae.

-- ChristineCargill - 24 Jan 2009

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DCC_836.2.gifgif DCC_836.2.gif manage 254 K 2009-04-23 - 10:53 ChristineCargill carolinianus 836.3
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Phaeoceros_paper2008.pdfpdf Phaeoceros_paper2008.pdf manage 1 MB 2009-04-26 - 12:52 ChristineCargill Descriptions of four Australian species of the hornwort Phaeoceros
engelii.gifgif engelii.gif manage 504 K 2009-08-29 - 19:01 ChristineCargill P.engelii distal spore
engelii2.gifgif engelii2.gif manage 593 K 2009-08-29 - 19:10 ChristineCargill P.engeli proximal spore
engelii3.gifgif engelii3.gif manage 556 K 2009-08-29 - 19:51 ChristineCargill P.engelii prox. 2
engelii4.gifgif engelii4.gif manage 624 K 2009-08-29 - 19:56 ChristineCargill P.engelii prox.4