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Isoetes Toximontana (Isoetaceae), a New Quillwort with Green Megaspores from the Northern Cape of South Africa

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Isoetes Toximontana (Isoetaceae), a New Quillwort with Green Megaspores from the Northern Cape of South Africa Isoetes toximontana (Isoetaceae), a New Quillwort with Green Megaspores from the Northern Cape of South Africa Lytton John Musselman Department of Biological Sciences, Old Dominion University, Norfolk, Virginia 23529-0266, U.S.A. [email protected] J. P. Roux Compton Herbarium, National Botanical Institute, Private Bag X7, Claremont 7735, South Africa. [email protected] ABSTRACT. Isoetes toximontana is only the second tata. Velum absente; parietes sporangii pellucidos. Megas- quillwort reported from the Northern Cape region porae paucae (usque ad 36 per sporangium), olivaceae, 275±320 mm in diam., in parietibus proximalibus distal- in South Africa. It occurs in shallow water on the ibusque, aeque tuberculatae, tuberculis altitudine varian- Gifberg. Megaspores are uniformly tuberculate on tibus, cingulo angusto sub crista aequatoria posito. Mi- the proximal surface; their distal surfaces may have crosporae brunneae usque ad 25 mm longae, aculeatae occasional rugi along with bullae. They are olive stelis remotis. green when dry. Microspores are brown and acu- Plants amphibious, emergent. Rootstock three- leate. Preliminary ®eld studies suggest that an un- sided. Roots simple. Leaves 3 to 10 per plant, dull expected diversity of quillworts is found in this re- green, stiff, spirally arranged, up to 42 mm long, gion. obtuse, ca. 0.5 mm wide at mid length, elliptic in Key words: Gifberg, Isoetaceae, Isoetes, North- cross section. Leaf epidermal cells with tuberculate ern Cape Province, Quillwort, South Africa. outgrowths, with four air chambers near the base, but these absent toward the leaf apex, with four Burrows (1990) recorded six species of Isoetes L. rows of stomata parallel to the air chambers, pe- from South Africa, with only two from the Cape ripheral strands lacking. Scales present. Megaspo- region (Cape Agulhus to the Namibian border): I. rophylls and microsporophylls on the same plant. capensis Duthie and I. stellenbossiensis Duthie. Velum absent. Sporangium wall clear. Megaspores Their presence as the only quillworts in the ¯ora is few (up to 36 per sporangium), gray-green in color, con®rmed in a recent comprehensive treatment of 275±320 mm diam., uniformly tuberculate on the the ferns and fern allies of the Cape (Roux, 2000). proximal surface, the distal surface with occasional Our report here of a new species is the ®rst quill- rugi. Tubercules of varying heights, with a narrow wort documented across this large geographical girdle below the equatorial ¯ange. Microspores area. brown en masse, to 25 mm long, aculeate with re- mote stelae. The name is derived from Gifberg, Af- Isoetes toximontana L. J. Musselman & J. P. rikaans for ``poison mountain,'' where the type was Roux, sp. nov. TYPE: South Africa. Northern collected. Cape Province: Gifberg, shallow water along Gifberg Road, 1 km S of Oubergpad, 318479090S, 188459710E, ca. 22 km SE of Van- Spore color, ornamentation, and size. Isoetes rhynsdorp, 565 m, 20 Sep. 2001, Lytton J. toximontana has green megaspores, a character ®rst Musselman & Elizabeth R. Musselman 2001- reported in the genus by Duthie (1929) for I. stel- 35 (holotype, NBG; isotype, MO). Figures 1, 2. lenbossiensis (Fig. 1B, D). It can be distinguished from other Southern African quillworts by mega- Planta amphibia, emergens. Excaudex trigonus et rad- icibus simplicibus. Folia usque ad 10, obscure viridia, spore ornamentation and leaf features. Isoetes stel- rigida, spiralia, usque ad 42 mm longa, apicibus obtusa, lenbossiensis has reticulate megaspore ornamenta- in medio longitudinis ca. 0.5 mm lata, in sectione trans- tion; I. capensis megaspores are boldly rugate on versali elliptica, cellulis epidermalibus omnibus proces- the distal surface. (Terminology for spore ornamen- sibus tuberculatis ornatis, prope basim folii tantum, cav- ernulis aeriis quatuor etiam seriebus stomatum ad as tation follows Lellinger & Taylor, 1997.) Based on parallelis praeditis, littis peripheralibus absentibus. Me- the ®gures in Burrows (1990), there are four quill- gasporophylla microsporophyllaque in eadem planta por- worts in southern Africa with tuberculate mega- NOVON 12: 504±507. 2002. Volume 12, Number 4 Musselman & Roux 505 2002 Isoetes toximontana from South Africa Figure 1A±E. ÐA. Roadside ditch with shrubby restio. Type location. ÐB. Megaspores. Brown microspores are evident on the surface. ÐC. Isoetes toximontana. Note the size of the plants. ÐD. Mixture of megaspores of I. toxi- montana (green) and Musselman & Musselman 2001-33 (white). ÐE. Representative plants of I. toximontana. The coin is ca. 2 cm in diameter. spores: I. giessi Launert, I. transvaalensis Jermy & crospores are brown (Fig. 1B) and have aculeate Schelpe, I. welwitschii A. Braun ex Kuhn, and I. macro ornamentation (Fig. 2C). Megasporophylls alstonii Reed & Verdcourt. Of these, only I. giessi and microsporophylls were found in mid September and I. welwitschii lack a velum. Isoetes welwitschii on the same plant. is more tropical in its distribution and in South Leaves. Unlike I. stellenbossiensis, the Gifberg Africa is known from only a few collections in the quillwort has stomata in rows on the adaxial surface eastern part of the country (Burrows, 1990). Quill- (Fig. 2B, F, G). Leaf epidermal cells have a dis- worts of Namibia are poorly understood, including tinctive ornamentation consisting of knobby out- the taxon known as I. giessi from central Namibia, growths (Fig. 2F, G). No peripheral strands (collen- which does have tuberculate megaspores. However, chyma-like cells) were found (Fig. 2D). ornamentation is sparse and megaspores are white. The size of megaspores and microspores of I. toxi- Rootstock and roots. The rootstock is three-sid- montana is similar to that of I. stellenbossiensis and ed (Fig. 2H). No branched roots, characteristic of I. capensis, both diploids (R. D. Bray, unpublished), most Isoetes species, were evident in I. toximon- suggesting that I. toximontana is also diploid. Mi- tana. 506 Novon Figure 2A±G. Isoetes toximontana. ÐA. SEM of megaspores. Scale 5 200 mm. ÐB. SEM of leaf tip. Note the rows of stomata on the adaxial side. Scale 5 100 mm. ÐC. SEM of microspores. Scale 5 10 mm. ÐD. SEM of cross section of leaf at midpoint. Arrow indicates stomatal apparatus. Scale 5 200 mm. ÐE. Megaspores of Musselman & Musselman 2001-33 with rugulate ornamentation. ÐF. Cross section of leaf of Musselman & Musselman 2001-33. Note the four air chambers. ÐG. Two stomata of I. toximontana. ÐH. Cross sections of rootstocks of I. toximontana. Volume 12, Number 4 Musselman & Roux 507 2002 Isoetes toximontana from South Africa Habitat. This diminutive species (Fig. 1C, E) croscopy and Alan Savitzky for light microscopy. was found only as a submergent in a temporary Discussions with Carl Taylor were helpful and en- pond dominated by a semi-shrubby restio (Restion- couraging. We thank him for sharing preliminary aceae) (Fig. 1A). Our preliminary ®eldwork in the data from his phylogenetic work on South African Gifberg, the southwestern-most escarpment of quillworts. Research was supported in part by the sandstone of the Cape System, indicates that sev- Mary Payne Hogan fund. eral taxa of quillworts may be present. One of these quillworts has white megaspores with rugate orna- Literature Cited mentation (Fig. 1D, 2E). At least one putative hy- Burrows, J. E. 1990. Southern African Ferns and Fern brid was found, distinguished by aborted spores, Allies. Frandsen Publishers, Sandton. another indication of the diversity of Isoetes taxa Duthie, A. V. 1929. The species of Isoetes found in the Union of South Africa. Trans. Roy. Soc. S. Afr. 17: 321± previously unknown in this part of southern Africa. 330. Preliminary molecular work using ITS sequences Lellinger, D. B. & W. C. Taylor. 1997. A classi®cation of indicates that I. toximontana is a distinct species spore ornamentation in the Pteridophyta. Pp. 33±42 in with nine unique substitutions located in a clade R. J. Johns (editor), Holttum Memorial Volume. Royal Botanic Gardens, Kew. with I. capensis (W. C. Taylor, pers. comm.). Roux, J. P. 2000. Pteridophytes. Ferns and Fern Allies. Pp. 37±50 in P. Goldblatt & J. Manning, Cape Plants. Acknowledgments. We thank Denise Wadsworth A Conspectus of the Cape Flora of South Africa. Stre- for preparing materials for scanning electron mi- litzia 9: 1±743..
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