Rubiacearum Americanarum Magna Hama Pars XII. A New Species of Ixora (Ixoreae) from Panama Charlotte M. Taylor Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166, U.S.A.
[email protected] The new species Ixora knrppine C. M.Taylor (Rubiaceae) from the San Bias region of Pan-ama, described and illustrated here, is notable forits opposite, subsessile, basally rounded to 'ordlateleaves. Key words: xo. or, Ireae. Mesoarnerica, Pan-ama, lHubliaceae. The pantropical genus Ixora I,. (Ixoreae: An-dtreason & Bremer. 2000) comprises about 300 to 400 species of shrubs and small trees found in moist and wet vegetation (De Block, 1998). The majority of Ixora species are found in Asia, alnd this genus is also well irepresented in Africa. Mad-agascar, and the Neotropics. Ixora has perhaps 30 Neotropical species. wxhere as noted by De Block (1998) it is quite poorly studied. Several Asian spe-cies are widely cultivated in tropical regions: a key to these was presented by Bridson (1988). Ixora has never been reviewed as a whole for the Neotropics. though it has been treated floristically for somen Neotropical regions, notably by Steyermark (1967, 1974). Ixora was long included in the tribe Pavet-teae (Robbrecht. 1993: 1)e Block, 1998), but more recent work (Andreason & Brenmer, 2000)) has shown that it is better placed in a separate Ixoreae. In the Neotropics Ixora is distinguished withinthe Rubiaceae by its stipules that are interpetiolar,narrowly triangular, generally persistent, and oftenalso shortly united intrapetiolarly; its calyx limbsthat are four-lobed with the lobes often narrowlytriangular to linear; its salverform corollas with thetubes generally glabrous internally: its corolla lolbesfour, elliptic to ovate, and convolute in aeslivation,its stamens four and usually inserted in the corollathroat on short filaments with the anthers partiallyexserted; its stigmas two, short, and exserted: itsovary bilocular with the ovules solitary in each loc'-ule anti apically attached; and its fleshy drupaceousfruits with the pyrenes two. planoconvex. generallysmooth dorsally (i.e., abaxially), and usually ratherthin-walled. The leaves lack domratia. of either fo-veolate or piilosulous form. The infloresceices aregenerally corymbilforn and bracteate, and may IbeNov\N 13: 216-219. 2003.terminal, cauliflorous. or ramiflorous. TIe fragrantflowers are honmostylous and generally white, vel-low, or red. In her excellent revision of Ixora inAfrica. De Block (1998) also highlighted the petiolebases, which are articulated from the stems (at leastin dried specimens) in Ixora. as a good characterfor recognition of this genus. This character isfumin in Neotropical Ixora species as well. OtherNeotropical Rubiaceae genera have not yet beenwidely surveyed for this feature: articulated petiolebases are known in a few other paleotropical gen-era, of several different tribes. The inflorescenceaxes of Ixora are also usually articulated, often giv-ing them a distinctive appearance when dry. The flowers of Ixora exhiiit an adaptation for pollination that is more comiion in Rubiaceae of the Paleotropics than the Neotropics. c'alled sec-ondary pollen ipresentation. The flowers of Ixora species are protandrous, and the anthers in bud are held closely aroulnd the style and stignmaic armns. Ratlier than presenting their pollen directly to pol-linators, the anthers release and transfer some or all of their pollen onto the upper part of the style and the Inon-receptive abaxial surfaces of the slig-lmatic arns. Thein this transferred pollen is exlposed to pollinators for some period of' tinme oni these structures: after this the stigmatic arms separate and the stigmatict surfaces becomei recepitive. The inflorescences of Ixorat are considered ter-miiial, niost often arising directly from tlhe apicesof thie main stemis but sometiiies borne on shortlateral stemns produced in the leaf axils. These lat-eral stemis are called short shoots bearing terminalinflorescences by I)e Block (1998). In solme Neo-tropical species tlie stem portion of tlhtse shortshoots mia be reduced so that the inflorescencesapipear to be axillary (e.g., I. .yaritensis Steyermark).The inflorescences of Ixora are usually regularlybranched with the higher ornder axes as well devel-opedl as the axis fronm which they branch: this con-dition was calletd "trichotomnous" bv I)e Blc'k(1998). The inflorescences may vary Iimarkedlyamongii species of Ixora in their deglree of expan-sion, ftrom strongly conlgested. with the axes only
Localities extracted from OCR text.
BioStor
