Asplenium
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Asplenium  |
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Family: Aspleniaceae  Patricia Sendao |
Spleenworts Latin asplenum, spleenwort; in ancient Greece the plants were believed to cure spleen diseases. Plants small to medium-sized, terrestrial or epiphytic. Fronds small to large. Rhizomes short-or long-creeping, decumbent or erect, apexes covered with clathrate scales. Stipes clustered to remote, usually flattened or grooved adaxially, black, purple, dark brown, tan to light green, smooth and often glossy, sometimes winged, usually scaly with clathrate scales at bases, sometimes with hairs and glands, cross section at base revealing 2 back-to-hack, C-shaped vascular bundles that join distally to form single X-shaped bundles. Blades variable, simple to 5-pinnate. Ultimate segments variable in shape and size, sometimes dimidiate. Veins free (except in A. nidus). Sori linear, borne along one or both sides of veins. Indusia linear, attached to veins. Asplenium is one of the world's largest fern genera, with more than 700 species. It is also the largest fern genus in Hawai 'i, where eight endemic and eleven indigenous species are found. In addition there are one endemic variety (A. peruvianum var. insulare) and one endemic subspecies (A. trichomanes subsp. densum) of species that lack the typical variety in Hawai 'i. Four hybrids are known and surely more hybrids and species will be found. No Asplenium species are known to have become naturalized. Hillebrand ( 1888) reported that Asplenium varians Hook. & Grev. (A. varians is now treated by some as a synonym of A. laciniatum D. Don) was native to Maui, citing collections by D. D. Baldwin. Several collections attributable to Baldwin are found at the National Herbarium in Washington, D.C., and at the Jepson Herbarium at the University of California, Berkeley. A single collection labeled "discovered for the first time in this locality by Miss E. S. Boyd in 1875 on the island of Maui," with no further information, is also in the Jepson Herbarium. Asplenium varians apparently has not been collected in Hawai 'i again in the past 125 years. Unfortunately specific location of its collection on Maui is not given on the collection labels. The status of this fern in Hawai 'i is unknown. It may have been a rare indigenous species, now extinct. It may have been a locally naturalized species that has since disappeared from the site where it was collected, or it may have accompanied other plants, such as bananas, brought to Hawai 'i from its native habitat (native to South Africa, Sri Lanka, India, Thailand, China, Japan, and Korea). It is unlikely that it was brought to Hawai 'i for its horticultural value. Asplenium varians has not been treated in the Asplenium key or the descriptions because so little is known about its status in Hawai 'i. Natural groups in Asplenium have been recognized as separate genera by some authors; some of these groups are Thamnopteris C. Presl, the bird's-nest fern (A. nidus), and Hymenasplenium Hayata, with thin, long-creeping rhizomes (A. excisum, A. unilaterale), representatives of which are found in Hawai 'i. The endemic Hawaiian genus Diellia has been included in Asplenium by one author. The Hawaiian Asplenium taxa may be grouped by origin as follows, although further study may reveal some supposed endemic species to be more widespread. Endemic Species and Infraspecific Taxa Asplenium acuminatum A. contiguum vars. contiguum and hirtulum A. haleakalense A. hobdyi A. horridum var. glabratum A. kaulfussii forms bipinnatum, dareoides, kaulfussii, and gemmiparum A. macraei A. peruvianum var. insulare A. schizophyllum A. sphenotomum A. trichomanes subsp. densum Indigenous Asplenium adiantum-nigrum A. aethiopicum A. excisum A. horridum var. horridum A. insiticium A. lobulatum A. monanthes A. nidus A. normale A.polyodon A. unilaterale Hybrids A. hobdyi X A. normale (=Asplenium xjlagrum) A. aethiopicum x A. polyodon ( = A. x kokeense) A. polyodon x A. sphenotomum (=A. xsphenocookii) A. acuminatum x A. aethiopicum (=A. xwaikamoi) Naturalized Species None Only two reviews of Hawaiian Asplenium (Hillebrand 1888, Robinson 1913) have been published. Hillebrand's treatment is excellent, but taxonomic and nomenclatural changes over the last 110-plus years have made it difficult to use. Robinson's descriptions are often inadequate, or lacking, and advances in knowledge have rendered her treatment obsolete. Species of Asplenium in Hawai'i, as elsewhere, are polymorphic and often poorly defined, with variable morphology, especially in the degree of frond cutting. In the past few decades several new Hawaiian Asplenium taxa have been discovered. In addition, multiple names have been applied to some species, resulting in much confusion as to which species are present, how many there are, and their status as endemic or indigenous species. Several species have been treated in this book as endemic, but further study may reveal some to be more widespread. The indigenous species have been treated here using a currently appropriate name, without vigorously attempting to determine whether some of them are in fact endemic or more widespread. A worldwide and a local review of the genus using new morphological features, chromosome studies, scanning electron microscopy of spores, isozyme and DNA work, and commongarden studies may eventually clarify the status and names of some Hawaiian species. KEY TO THE SPECIES OF ASPLENIUM IN HAWAI'I 1. Blades simple, sessile; veins anastomosing distally to form continuous marginal commissural veins; sori to 9+ cm long; plants resembling shuttlecocks; all major islands ............................... 14. A. nidus 1. Blades 1-pinnate to 5-pinnate; veins free, without marginal commissural veins; sori less than 3 cm long; plants not resembling shuttlecocks (2). 2(1). Rhizomes less than 4 mm diam., long-creeping; fronds well separated on rhizomes; blades 1-pinnate; pinnae thin, membranous, strongly dimidiate (3). 2. Rhizomes thicker than 5 mm diam., creeping, decumbent to erect; fronds clustered at tip; blades 1- to 5-pinnate; pinnae chartaceous, herbaceous to coriaceous, not membranous, not asymmetrical (dimidiate), or weakly to strongly dimidiate (4). 3(2). Fronds mostly 25-55 x 5-11 cm, tips mostly abruptly reduced, narrow, almost tail-like, pinnae usually more than 3 X 0.8 cm; proximal 112 of lower margins of pinnae moderately to strongly concave, upper margins with coarse teeth often paired on small projections; all major islands ............................................... 5. A. excisum 3. Fronds mostly 15-35 x 2-4.5 cm, tips gradually or abruptly narrowed; pinnae usually less than 2.5 x 0.7 cm; lower margins of pinnae nearly straight to moderately concave, upper margins with fine teeth; all major islands ............................................ 21. A. unilaterale 4(2). Blades 1-pinnate to 1-pinnate-pinnatisect (5). 4. Blades 2- to 4-pinnate (16). 5(4).Blades usually less than 5 cm wide (6). 5. Blades usually more than 6 cm wide (11). 6(5). Rachises gray brown, dull; adaxial surface of stipe with green ridges (7). 6. Rachises black, dark brown, or dark purple, shiny; ridges absent (8). 7(6). Largest pinnae usually more than 10 mm long, somewhat pointed, highly variable in shape, almost rectangular with entire margins, acroscopic margin with 5-8 lobes, to deeply lobed, to 2-pinnate; fronds never proliferous; sori usually more than 8 per pinna; plants of mesic or wet forests; all major islands ....................................... 12. A. macraei 7. Largest pinnae mostly less than 6 mm long, tips blunt, uniform in shape, shallowly lobed, 2-5 lobes on acroscopic side; fronds with distal stipes and proximal rachises occasionally proliferous; sori less than 5 per pinna; plants of dark caves or lava tubes; Maui, Hawai'i ................................. 16. A. peruvianum var. insulare 8(6). Proliferations almost always present on distal halves of rachises; pinnae somewhat asymmetrical (subdimidiate); acroscopic margins entire to shallowly crenate; sori 1-8 per pinna (9). 8. Rachises never proliferous, or occasionally proliferous only at distal portion of stipe or proximal portion of rachis or on pinnae; sori 1-4 per pinna ( 1 0). 9(8). Fronds with 1 proliferation at tips of rachises, terminating them, proliferation enveloped by 2 distal pinnae; middle pinnae 6-22 mm long; vein endings 9-20 on middle pinnae; pinna tips rounded to pointed; plants of mesic to dry forests; all major islands ............................. 15. A. normale 9. Fronds with 2-6 proliferations on distal rachises, frond tip extending beyond most distal proliferation, not enveloped by 2 distal pinnae; middle pinnae 4-14 mm long; vein endings 2-5(-6) on middle pinnae; pinnae tips rounded or almost truncate; plants of very wet, dark places; Kaua 'i, Moloka 'i, Maui, Hawai 'i . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. A. hobdyi 10(8). Rhizome apexes surrounded by numerous dark brown, shiny old stipe bases; pinnae ovate to round, not or only slightly dimidiate; sori 1-4 on each side of midrib; fronds never proliferous ..... 20. A. trichomanes subsp. densum 10. Rhizome apexes surrounded by only a few, if any, old stipe bases; pinnae strongly dimidiate; sori mostly 1(-2) per pinna usually along the lower margins (occasionally more and on distal margin); occasionally proliferous on proximal rachises or distal stipes; Maui, Hawai 'i ..... 13. A. monanthes 11(5). Plants almost always proliferous at distal part of rachises; all major islands ............................................. 11. A. lobulatum 11. Plants mostly not proliferous, or if proliferous, proliferations occurring on lateral veins of several pinnae (12). 12(11). Blade tips resembling lateral pinnae, not pinnatifid; plants sometimes 12. Blade tips pinnatifid; plants never proliferous (13). 13(12). Ultimate segments fan-shaped or nearly so, particularly the acroscopic basal segment or lobe; veins spreading fanlike, without central axis; all major islands ..................................... 3.A. aethiopicum 13. Ultimate segments of various shapes, rarely fan-shaped (14). 14(13). Pinnae deeply lobed, margins smooth to dentate at tips; stipes and rachises very scaly (except var. glabratum); glandular hairs absent; all major islands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8. A. horridum 14. Pinnae entire, or shallowly to deeply lobed, some basal pinnae cut to costae, making the fronds 2-pinnate at bases, margins serrate or dentate; stipes and rachises glabrous to sparsely scaly except at very bases; glandular hairs present or absent (15). 15(14). Sori diverging from costae, curving out l/2-2/3 the way to margin; blades variable, mostly 1-pinnate (sometimes 1-pinnate-pinnatisect,_ 15. Most sori close to and parallel with costae; blades 1-pinnate; pinnae entire with long, acuminate, narrow tips, not lobed (occasionally cut into narrow lobes); plants usually epiphytic, sometimes terrestrial; all major islands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4. A. contiguum 16(4). Rachises almost always proliferous near tips (17). 16. Rachises never proliferous (18). 17(16). Blades mostly 3-pinnate; all major islands ................. 19. A. sphenotomum 17. Blades 2-pinnate only at very base, otherwise 1-pinnate-pinnatifid; all major islands except Uina'i ...... : ....................... 9. A. insiticium 18(16). Stipes and rachises of different colors: lower stipes dark brown, shiny; distal rachises light green, dark color gradually tapering to a point in distal stipes or on rachises, clearly delineated from adjacent light green color; all major islands ........................................ 2. A. adimitum-nigrum 18. Stipes and rachises of uniform color (19). · 19(18). Stipes 0.8-1.2 mm diam. near base, dark brown with raised, narrow, greenish longitudinal ridges on adaxial surface; all major islands ....... l2.A. macraei 19. Stipes 1.5-5.5 mm diam. near base, brown to dark brown, without ridges(20). 20(19). Blades 2-pinnate (occasionally 2-pinnate-pinnatifid in A. aethiopicum and A. haleakalense) (21). 20. Blades 3- to 4(-5)-pinnate (22). 21(20). Ultimate segments short-stalked, oblong-lanceolate, tips often acuminate, slightly lobed (especially acroscopic base); blades always 2-pinnate; all major islands ....................................... l. A. acuminatum 21. Ultimate segments not stalked, fan-shaped or nearly so, particularly the acroscopic basal segment; blades variable 1- to 2-pinnate pinnatifid; all major islands ..................................... 3.A. aethiopicum 22(20). Blades 4(to 5)-pinnate, to 75 cm long; proximal stipes glabrous; ultimate segments mostly 1-2 mm wide, usually with 2 obtuse teeth; Kaua'i, Hawai 'i ......................................... 18. A. schizophyllum 22. Blades usually 3-pinnate, to 45 cm long (usually shorter); proximal stipes with scattered, minute, appressed glands; ultimate segments 2-4 mm wide, unforked or forked into l-3 lobes with blunt tips and l-3 rounded teeth; East Maui. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. A. haleakalense |
