Ixia acaulis, a New Acaulescent Species of Iridaceae: Ixioideae from the Knersvlakte, Namaqualand, South Africa Peter GoldblattB. A. Krukoff Curator of African Botany, Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166, U.S.A. John C. ManningCompton Herbarium, National Botanical Institute, Kirstenbosch Botanic Gardens, Claremont 7735, South AfricaABSTRACT. The generic placement of a new spe-cies, Ixia acaulis, from limestone outcrops in theKnersvlakte, Vanrhynsdorp District, South Africa,is not immediately clear in part due to its reducedacaulescent habit. The bright yellow flowers have asubterranean ovary and are borne above groundlevel on a long perianth tube. An acaulescent habitis unusual in Iridaceae, although known in severalgenera of the two larger subfamiles, Iridoideae andlxioideae. In an effort to correctly assign the plantto a genus, we have examined leaf anatomy andchromosome cytology as well as macromorphologyand palynology. A basal rooting corm places thespecies firmly in Ixioideae, as does the perforateexine sculpturing. We conclude that it belongs inthe southern African genus Ixia, although an acau-lescent habit is otherwise unknown in this genus andother aspects of the plant do not exactly conformto this genus. The uncertain generic position of a new speciesof Iridaceae subfamily Ixioideae from the Knersv-lakte north of Vanrhynsdorp, Cape Province, SouthAfrica, required detailed investigation of its mor-phology, leaf anatomy, cytology, and palynology. Itis unusual in the subfamily in lacking an aerial stem.The flower has a subterranean ovary and is raisedabove the ground by means of a long perianth tube.Finely fibrous corm tunics seem to preclude anyrelationship with Ilesperantha, Romulea, or Syr-ingodea, in which acaulescence is the rule or atleast not uncommon, but in which the corm tunicsare more or less woody. However, a combination ofreduced and specialized features makes it uncertainwhether the species belongs in Ixia, Tritonia, Spar-axis, Anomatheca, or Duthieastrum, all of whichhave fibrous corm tunics, but only the last is nor-mally acaulescent.NovoN 3: 148-153. 1993.MORPHOLOGYVEGETATIVE ORGANIZATION The small plants (Fig. 1 A, B) grow singly or insmall clumps, each individual consisting of an elon-gate, more or less symmetrical, round-based cormwith fibrous corm tunics (Fig. 1 B) that accumulatein older plants to form a thick matted fibrous layer.The corms produce roots from the basal area butin no particular pattern. The 3-5 foliage leaves arebasal and sheathed below the ground by 2 mem-branous, entirely sheathing cataphylls. The leaf bladesare equitant and more or less linear. Under naturalconditions the blades are more or less prostrate onthe ground. Although the blades are unifacial, thereis no morphological or anatomical differentiation be-tween the leaf surfaces facing toward or away fromthe surface of the ground. Grown under greenhouseconditions with more water than normally available(as were the plants illustrated), the leaves tend tobe inclined rather than prostrate. The stem is short,1-2 cm long, but does not reach ground level atanthesis and bears one or occasionally two flowers.As the capsules ripen the peduncle elongates so thatthe seeds are released at ground level.FLORAL STRIUCTIRHE The flowers are sessile (i.e., lack pedicels) andare subtended by a pair of opposed membranousbracts inserted at the base of the ovary (Fig. 1C,G), thus conforming to the pattern in all lxioideae.In the three other subfamilies of Iridaceae the flow-ers are normally pedicellate, rarely sessile, and al-ways subtended by a single bract (Goldblatt, 1990).Also typical of Ixioideae, the outer bract is largerthan the inner in Ixia acaulis, although the twobracts are more or less equal in length (Fig. 1G).The inner bract is 2-veined and apically forked. The
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