Myrcia amazonica DC.

Authority

Maguire, Bassett. 1969. The botany of the Guayana Highland-part VIII. Mem. New York Bot. Gard. 18: 1-290.

Family

Myrtaceae

Scientific Name

Myrcia amazonica DC.

Discussion

Myrcia corymbosa DC., Prodr. 3: 252.1828

Aulomyrcia amazonica (DC) Berg, linnaea 27:41.1855

Myrcia amazonica de Candolle, DC. Prodr. 3: 250. 1828.

Myrcia corymbosa DC, DC. Prodr. 3: 252. 1828.

Aulomyrcia amazonica (DC.) Berg, lAnnaea 27: 41. 1855.

Myrcia paraensis (Berg) Kiaersk., Enum. Myrt. Bras. 78. 1893.

Myrcia hostmanniana (Berg) Kiaersk., Enum. Myrt. Bras. 83. 1893.

After examination of a number of types and isotypes in European herbaria in 1954, I prematurely reduced several Candollean and Bergian species to the synonymy of Myrcia amazonica (cf Field Mus. Publ. Bot. 13(4): 628. 1958). N o w after examination of much additional material from eastern and northern South America I am less sure of specific limits than I was a decade ago, but perhaps better able to distinguish between species-groups. In 1966 I was permitted to restudy the Candollean types in Munich. It transpires that M . elegans, M . lauriflora, M . spixiana, Aulomyrcia pruinosa and A. poeppigiana belong not with M . amazonica but with M. guianensis. Myrcia nigrescens proves to be a synonym of Marlierea umbraticola; of all the species reduced to synonymy under M . amazonica in 1958, only M . corymbosa, A. paraensis and A. spruceana remain.

As I now understand Myrcia amazonica, it is a plant of eastern South America and the Amazon basin, with glabrous or nearly glabrous leaves that tend to darken in drying, the midvein impressed above, the inflorescence reddish-pubescent with deciduous bracts, the hypanthium and the whole bud glabrous except that the calyxlobes m a y be ciliate, the calyx-lobes 5, very short and all about the same size, glabrous or thinly strigose on the inner surface, the small globose fruits 4-6 m m in diam, and the ovary bilocular. The type-material, at M , includes 3 sheets with many mature or nearly mature fruits; the lectotype, annotated by de Candolle, is represented by Field Mus. neg. 19753. In all the ^Decimens the young branchlets are sparingly reddish- or sordid-strigose, and the channeled petiole is strigose in the channel and at the base of the impressed midvein; the leaves are smooth, glabrous on both sides, not impressed-punctate; the inflorescence is thinly pale reddish-pubescent; the calyxlobes are 5, persistent and unbroken on the fruit, a little unequal, triangular-obtuse, up to 1 m m wide and less than 1 m m long, thinly yellowish'-strigose on the inner surface.

In eastern South America, especially in the Guianas, plants of this species-complex have passed mostly under the name of Aulomyrcia hostmanniana. Among the numerous specimens available for study there is relatively little variation. Forms with relatively blunt, coriaceous leaves occur; the foliage and calyx-lobes may be quite glabrous, or as often pubescent in the manner of Myrcia amazonica; the calyx-lobes may be equal or slightly unequal. I cannot find any characters by which M . hostmanniana may be upheld. The specimens cited by Berg under .Aulomyrcia hostmanniana a robustior were "Guiana AngHca (Rich. Schomb., coll. no. 1054), nee non in Guianae Batavae prov. Para (Wullschlaegel, coll. no. 199)," "v. in herb. Berol. et Martian." Under /S gracilior he cited "in Guiana Batava (Hostmann, coll. no. 881. 755)," "v. in herb. Berol., Sender., Vindob." The two varieties, according to Berg, differ chiefly in the length and stoutness of the panicles. I have seen all the cited gatherings except that of Wullschlaegel, and in m y opinion they represent the same species. It seems appropriate, as Berg indicated no preference, to designate the most widely distributed collection, Hostmann 881, as the type of the name .1. hostmanniana and therefore the type of the name ß gracilior. A sheet of no. 881 at W is designated as lectotype"

isotypes have been seen at W, BM, G, K; Amshoff cites the same collection from N Y , P, and U. A paratype, Hostmann 755 ( W ) , is named /3 gracilior by Berg. The Schomburgk collection cited under a robustior, no. 1054, was presumably at Berlin, and is assumed to have been destroyed; a sheet of the same number is at K, ex herb. Berol., named a robustior by Berg, and a second sheet at K is numbered 698/1054B, indicating that these numbers, in accordance with the numbering system used by the Schomburgk brothers (see the introduction to this paper), refer to the same gathering. A sheet of no. 698 at W , named by Berg as a robustior, doubtless represents the same gathering. Two other species cited above in synonymy, Aulomyrcia paraensis and A. spruceana, are known to m e from the types only. The type of A. paraensis {Spruce 824, at ^I) is from Santarem, Para. The plant is mostly in bud. In pubescence of leaves and calyx and in general appearance it is very similar to Myrcia amazonica. The type of A. spruceana {Spruce 1172, or "Myrcia 16," at M ) , is from Barra, near the mouth of the Rio Negro; it resembles the types of M . amazonica and M . paraensis except that the pubescence is somewhat more abundant. Amshoff, in the Flora of Suriname, recognized Aidomyrcia leptoclada (DC.) Berg {Myrcia leptoclada D C , D C . Prodr. 3: 244. 1828) as a species ranging from the West Indies through the Guianas to Para. She said (Fl. Suriname 3(2): 82. 1951), "Perhaps not sharply distinct from A. Hostmanniana Berg." She distinguished the two as follows:

Sepals subequal, all shorter than 1 mm. A. hostmanniana.

Sepals distinctly unequal, the largest 1-1.5 m m long, often petaloid. A. leptoclada.

In the whole group of species including Myrcia amazonica, M . leptoclada, and M. hostmanniana, the calyx-lobes tend to be somewhat unequal, although the differences between the larger and smaller lobes are not so great as in the gorup that includes M . inaequiloba and its relatives. In the type of M . amazonica, for example, the lobes vary from about 0.3 m m to 0.7 m m in length; in the type of M . leptoclada (which is in bud only), the lobes are somewhat but not markedly unequal, 0.5 m m long or a little more. In most specimens of what has been called M . hostmanniana from South America and in many specimens from the West Indies, the range of variation is no more than the above; in the very similar Central American population that was described as M . gentlei Lundell, the inner calyx-lobes are often conspicuously thinner, larger and more petaloid. This feature in itself does not seem to provide a clear guide to the differentiation of species.

The type of Myrcia leptoclada, which' I studied at G - D C in 1966 (cf Field Mus. neg. 33488) is very similar to South American material of M . amazonica except that the inflorescence is essentially glabrous, even though the young herbage and leafy branchlets are appressed-pubescent with reddish hairs. The calyx-lobes are closely pubescent on the inner surface, like those of M . amazonica. Other West Indian collections that resemble the type in having the inflorescence glabrous or essentially so are from St. Vincent, Eggers 6988 (P), and from Guadeloupe, Duss 563 (P). South American collections on the other hand, including those from Trinidad, e.g., Eggers [ed. Rensch] 1157, at P, almost invariably are conspicuously if not always densely pubescent. On the basis of the rather limited material now available, it seems that the true M . leptoclada does not occur in South America.

Distribution

E N E Z U E L A . Amazonas: Rio Ventuari between Rio Paru and Las Carmelitas,elev 150 m, 19 Feb 1951 (bud). Cowan & Wurdack 31578 ( M I C H ) . Bolivar: Mt.Roraima District, Arabupu, elev 1300 m, 12 Dec 1938 (fl), Pinkus 58 (F, G, N Y ) ; km 27 S of El Dorado, elev 210 m, 25 Jul 1960 (fl), Steyermark 86630 (MICH);Rio Ikabaru, cerca del Campo Diamantifero de Uaiparu, elev 400-450 m, 16 Apr1957 (bud), Bernardi 6579 ( N Y ) . B R I T I S H GUIANA. Roraima, Schomburgk698 (MICH, W ) ; Ituni road, Mac

Venezuela South America| Guyana South America| Suriname South America|