(1965) (Euphorbiaceae) [Botanical Museum And
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Acta Botanica Neerlandica 14 (1965) 323-365 A Revision of the Genus Meineckia (Euphorbiaceae) Grady+L. Webster [Botanical Museum and Herbarium, Utrecht )* {received April 22nd, 1965) Abstract A revision ofthe Meineckia has resulted in the Euphorbiaceous genus recognition of 19 species, with 7 subspecies and 2 varieties (for a total of 25 distinct taxa). 5 and 1 Proposed as new are species subspecies, whilenew combinationsare necessary for 14 species and 6 subspecific taxa. The extraordinary confusion in the taxonomic of the is illustrated the fact 14 history genus by that the previously recognized species have been classified under 6 different generic names; Cluytiandra, Flueggea, and Neopeltandra, Peltandra, Phyllanthus, Securinega. As revised, the number of species different and Arabia, 4; represented in the regions is as follows: America, 3; Africa India and 4. The be ofAfrican Madagascar, 8; Ceylon, genus appears to origin and is probably most closely related to Zimmermannia. Introduction At this point in the Twentieth Century, botanical exploration has reached the stage where few really distinct new generaof angiosperms and await discovery outside such exotic places as New Guinea Mada- gascar. However, there is still a considerable amount of exploration to be done the mountains ofliterature herbarium collections among and amassed during the past two centuries. Some perfectly distinctive of in this genera flowering plants are about as effectively hidden systematic labyrinth as if they were growing atop the sandstone peaks of he Guiana Highlands. Such, at least, has been the fate of the Euphor- biaceous which until been genus Meineckia, now has never recognized in its entirety. Most of Meineckia and representatives are inconspicuous or rare, none appear to have been described prior to 1852, when Wight established the Peltandra basis of Indian genus on the two species. The taxonomic ofthe since then has been of whole- history genus one sale confusion and after obscurity. Baillon (1858), only six years Meineckia the basis of Arabian Wight, proposed a new genus on an plant collected by Botta, but incorrectly described the flowers as in fact petaliferous. Mueller (1865), noting that the flowers were apetalous, reduced Meineckia to a synonym of Flueggea, and in his treatment in the “Prodromus” (1866) transferred the single Arabian species to Securinega. * Present Address; Dept, of Biological Sciences, Purdue University, Lafayette, Indiana, U.S.A. 323 324 G. L. WEBSTER Meanwhile, Mueller (1863) had demotedWight’s Peltandra to the rank of a section of while later he created Phyllanthus, a year (1864) a for collected new genus Cluytiandra an Angolan species by Welwitsch, without between the Indian apparently suspecting any relationship and African plants. In Mueller’s revision in the “Prodromus” (1866) the known of thus species Meineckia were disposed under four different taxa: Cluytiandra, Phyllanthus sect. Peltandra, Securinega sect. Flueggea, and Securinega sect. Gelfuga. Part of the reason for this taxonomic mal- practice may lie in the fact that Wight had failed to observe the pistil- lode in the male flowers ofthe Indian species, and omitted it from his illustrations. Although Mueller detected the pistillode in the male flower of he did notice it in Phyllanthus neogranatensis, not appear to did Hooker Pax the Indian species, nor (1887) or Gamble (1925). Hoffmann of the and (1922), in a treatment supposedly entire genus Cluytiandra, actually discussed only the African species. Gamble (1925) realized that the Indian species assigned by Mueller and by Hooker to Phyllanthus sect. Peltandra did not really belong in Phyllanthus. Knowing that the generic name Peltandra Wight was Peltandra he preoccupied by Raf., proposed a new generic name, Neopeltandra. During the past 40 years, as a result of these breakdowns in taxonomic communication, the taxa of Meineckia have masqueraded under the entirely different names on various continents: as Phyllanthus in North America, Phyllanthus and Securinega in South America, Phyllanthus and Cluytiandra in Africa and Madagascar, and Neopeltandra in India and Ceylon. This thoroughgoing parochialism in treatment has obscured the of the its effectively geographical range genus, coherence as a phyletic unity, and its relationship to other taxa in the Euphorbiaceae. Examinationof the herbarium material of the taxa discussed below all in clearly indicates that they belong together a single genus distinct from Phyllanthus because of the annular disk and pistillode of the male flower, and from Securinega by virtue of the fused filaments and the Baillon’s characteristic pitted seeds. At generic level, name later Meineckia clearly has priority over Cluytiandra ; even though he followed Mueller in Meineckia to of (1874) reducing a synonym Securinega, it must be adopted. Conservation of the name Cluytiandra does since of the 19 herein not appear warranted, (1) only 5 species have heretofore received the under accepted proper combinations the is and the that name; (2) genus not economically important; (3) used in and generic name has scarcely been except certain African Malagasian floristic manuals. Morphology The species of Meineckia are shrubby plants which rarely exceed 4 or forms of M. and M. 5 m in height; some phyllanthoides parvifolia are very The nearly herbaceous. stems are usually slender and often zig-zag, be deci- with strictly distichous phyllotaxy. The foliage may either duous but in the aberrant or evergreen, except Madagascar species REVISION OF THE GENUS MEINECKIA (eUPHORBIACEAE) 325 M. orientalis, the leaves are thin and even membranous. Most of the taxa are monoecious, except for the Central American M. bartlettii and of is some the Madagascar species. It not always easy to determine whether is monoecious a species or dioecious, since sometimes the male flowers first and have fallen off the time appear may mostly by fruits the female are maturing. Fortunately, pedicel leaves a distinct basal in that it is sometimes deter- stump many species, so possible to mine the monoecious or dioecious condition even from barren speci- mens. Flowers of Meineckia are typically produced in axillary clusters which reduced the first flower represent cymules, (basal or central) being female male. and all the others Only very rarely are female flowers found paired at the axils; isolated instances have been found in M. phyllanthoides, M. parvifolia, and M. trichogynis. The pentamerous calyx is the monotonously similar in nearly all species, calyx-lobes having a single usually unbranched midvein. The annular floral disk, which is at least partially adnate to the calyx, is thin and shallowly cupuliform in most species, although in M. calycina it is thickened and fleshy. The androecium is all very characteristic, as in species the filaments are united for their This at least % or % lengths into a staminal column. column is adnate to the pistillode, so that only the upper part of the pistillode is visible above the end of the column; in descriptions, measurements of the pistillode refer only to this free portion. In in flowers which the filaments are fused only about halfway, they above the and it then be overlooked project pistillode, may easily (especially where it is minute, as in some of the Indian taxa). The anthers the are attached above base and are thus nearly versatile, with a more or less extrorsely lateral dehiscence. The pollen grains are not much those in various of exceptional, resembling unspecialized genera Phyllantheae, as indicated by Punt (1962). In all taxa examined, the rather with grains are tricolporate, finely reticulate, a fairly conspi- cuous costate colpus transversalis. There is not much difference in the in the with the size, mean length species largest grains (M. neogra- 39.7 32. for the of M. natensis) being p compared to grains calycina. The female flower of Meineckia is outstanding chiefly because of its elongated, slender, often channelled, stramineous pedicel which is usually articulated somewhat above the base. This basal portion, here the 0.5-3.5 designated as podium, is about mm long and usually darker than the it pedicel proper; may persist as a noticeable stump after dehiscence of the The is fruiting pedicel. ovary invariably glabrous, 3-carpellate, each carpel with 2 anatropous ovules. The styles in most taxa are bipartite or at least deeply bifid, and the slender terete style- branches are usually capitate. The capsular fruit of Meineckia ordinarily contains only 3 seeds at ovule in each maturity, one locule aborting during development. fruits with seeds locule the However, 2 per occasionally occur on same has in M. plant as capsules with solitary seeds; this been observed fruticans and M. humbertii, and may be tound in some ot the other species well. The seeds of in as Meineckia are especially characteristic and fact 326 O. L. WEBSTER the best feature for the Due to present single diagnostic genus. unequal growth—the abaxial side of the ovule far outstripping the adaxial (funicular) side—the seed assumes a distinctly reniform outline at maturity. The micropylar and chalazal ends are both beaked and convergent over the raphe, which lies in a semicircular recess on the ventral side of the seed. Theseed-coat is deeply and rather evenly pitted (shallowly pitted only in 2 Indian species), with the pits making deep indentations into the endosperm. When the seed is soaked in water the beaks straighten out and the pits become shallower, but the general remains One that the configuration unchanged. might suppose pitting represents an adaptation forrapid penetration ofwater, but in fact the seeds of Meineckia do take in faster than not appear to water noticeably the unpitted seeds of other Phyllantheae. The embryo is typical for broader and many Phyllantheae, with thin cotyledons considerably somewhat longer than the radicle. Relationships Among the poorly understood welter of taxa in the Phyllantheae, Meineckia stands out as a comparatively well-defined genus; its recog- nition of future taxonomic with appears justified regardless changes the of such regard to circumscription genera as Andrachne, Flueggea, Savia, and Securinega.