Monographs Details: Myrcia guianensis (Aubl.) DC. var. guianensis
Authority: Maguire, Bassett. 1969. The botany of the Guayana Highland-part VIII. Mem. New York Bot. Gard. 18: 1-290.
Family:Myrtaceae
Discussion:

(syn. M. elegans D C , M. exsucca D C , M. lauriflora D C , M. spixiana D C , M. obtusa Schauer, M. surinamensis Miq., .4. roraimensis Berg, .4. schomburgkiana Berg, .4. pruinosa Berg, A. gardneriana Berg, .4. androsaemoides Berg, .4. buxizans Berg, M. roraimae Oliv.).

Berg recognized five varieties of Aulomyrcia obtusa; Amshoff (Fl. Suriname 3(2): 77-79. 1951) recognized five, including the nomenclaturally typical variety, two of those described by Berg, and two new ones. Amshoff concluded her treatment of A. obtusa with the words, "The above described varieties are sometimes merging into each other." In m y opinion this is an understatement; I cannot recognize any taxonomic entities on the basis of the characters adduced by Berg and Amshoff. The so-called varietal differences, depending upon leaf-shape, length of panicle and number of flowers, and relative density of pubescence, seem to reflect individual variations in a large population. The form prevailing in northeastern South America is one with many or all of the larger and more vigorous leaves shortly and bluntly acuminate, the blades mostly 1-2 cm wide and 4-6(-10) cm long; the leaves on flowering branchlets are often shorter and obtuse, but usually elliptic rather than cuneate-obovate, and rounded at base. In the type of Aulomyrcia obtusa a grandifolia Berg (Suriname, Splitgerber s n, at W ) , the leaves are obovate, up to 6 cm long and 4 cm wide. Most plants are pubescent to some extent, and some densely so; many individuals, on the other hand, especially among the Amazonian populations, are nearly glabrous. It is possible that there is some correlation between the lack of pubescence and the occurrence of obtuse, obovate-cuneate (as opposed to acuminate, oblong-elliptic) leaves, but I cannot be sure of this. The apparent correlation may be a reflection of coUectors' choices of one leaf-form or another. The type of Myrtus pyrifolia J.-St. Hil., which I studied in Lamarck's Herbarium (P) in 1966, is labelled "de Cayenne, le Blond." It is a good average specimen of what I take to be one of the Guiana populations of Myrcia guianensis. The type of Myrcia elegans D C , which I studied at Munich in 1966, is only sparingly pubescent, but all the leaves on one (flowering) branch, and about half of the leaves on the other branch, are of the acuminate {"guianensis''') type. The specimen is taxonomically "atypical" of M. guianensis var guianensis, in that it is less pubescent than most individuals from Venezuela and the Guianas, and some of the leaves are obtuse and cuneate. In spite of these aberrant tendencies, the type seems clearly to belong with the population that ranges to the north of the Amazon, not with the blunt- and coriaceous-leaved plants that seem to be more common in the states of Ceara, Paraiba, Bahia, etc. The name Aulomyrcia schomburgkiana was based on "Rich. Schomb., coll. no. 1086" from British Guiana, and "Rob. Schomb., coll. no. 701," said to have come from Roraima. Berg saw these "in herb. Berol. et Vindob." A sheet of no. 1086 is at Kew, received from Berlin in 1859 and named by Berg; another sheet at Kew is numbered 701/1086B; according to the numbering system used by the Schomburgk brothers (see the introduction to this paper), it seems clear that Berg saw Rich. Schomburgk's no. 1086 at Berlin. It is assumed that this specimen has been destroyed. The specimen of no. 701 at W , named by Berg, is designated as a lectotype; additional isolectotypes have been seen at G, M I C H , and P. I should refer all the specimens to Myrcia guianensis. In the protologue of Aulomyrcia roraimensis. Berg cited "ad Roraima . . (Rich. Schomburgk, coh. no. 1117; Rob. Schomb., coll. no. 737)" and stated "v.s. in hb. Berol. et Vindob." A sheet at Kew is numbered 734 [sic]/1117B, and another sheet at K e w is Rich. Schomburgk 1117, named by Berg, received from Berlin in 1859. It is probable that Berg saw no. 1117 at Berlin; presumably the specimen has been destroyed. A sheet of no. 737 at W , named by Berg, is hereby designated lectotype; duphcates of this number are at B M , and M I C H . The plants on all these sheets are referable to Myrcia guianensis. Another species that is apparently a part of this complex is Aulomyrcia poeppigiana Berg [=Myrcia yungasensis Rusby], which I treated in the Flora of Peru (Field Mus. Pub. Bot. 13(4): 663. 1958) as a segregate from Myrcia amazonica D C , but which I now know to be quite a different species. I can find no way to distinguish Bolivian, Brazilian, and Colombian specimens of A. poeppigiana, including the type, from the average Guiana plant of M . guianensis. The following are presumably to be referred to A. poeppigiana {M. yungasensis). BOLIVIA. Mapiri region, San Carlos, elev 850 m, Dec 1926 (bud), Buchtien 952 (iNlICH); Apolo, 4800 ft, 22 Jul 1902 (fl, fr), Williams 1490 (MICH). BRAZIL. Falls of Madeira, Oct 1886 (fl), Rusby 603 (MICH); Ega, Poeppig 2834 (MICH, isotype of A. poeppigiana). COLOMBIA. Caqueta: 7.5 k m N N E of Solano, elev 200 m, 9 Mar 1945 (fl). Little & Little 9707 (MICH). Boyaca: Los Llanos, Mercedes on Cario Canacabure, elev ca 180 m, 20 Feb 1939 (bud), Haught 2618 (MICH, US). ]\Ieta: Llanos, elev 500 m. Mar 1948 (fl), Sandeman 5894 ( B M ). The following specimens seem to be referable to Myrcia guianensis var guianensis. V E N E Z U E L A . Delta Amacuro(?): Santa Catalina, M a y 1896 (fl), Rusby & Squires 250 (MICH). Amazonas: Cerro de la Neblina, Rio Yatua, elev 1900-2100 m, 18-19 Dec 1957 (bud), Maguire et al 42441 (MICH); great rapids of the Orinoco, near Puerto Ayacucho, elev 100-120 m, 18 Feb 1954, Maguire et al 37712 (bud, :^IICH), 37713 (imm fr, N Y ) ; Sabana Manacal, Rio Atabapo 15 k m above Guarinumo, elev 125 m, 12 Jun 1959 (fl), Wurdack & Adderley 42950 (MICH). Bolivar:' San Mateo, Bajo Paragua, elev 80 m, 9 Apr 1940 (bud), Williams 12808 (F); W end of El Pao (Iron Mines Co. of Venez. ore body), 1 M a y 1953, Maguire 35791 (fr, N Y ) , 35792 (fl, M I C H ) ; Altiplanicie de Nuria, SE of Hato de Nuria, elev 400 m 25 Jan 1961 (fr), Steyermark 88803 (MICH; det.?; ovary bilocular?); Altiplanicie de Nuria, 45 k m N of Tumeremo, elev 600-650 m, 5-8 Feb 1961 (imm fr), Steyermark 89136 (MICH). BRAZIL-VENEZUELA. Rio Branco-Bolivar: Serra do Sol, Rio Cauairan, elev 950 m, 16-18 Dec 1954 (fl), Maguire 40346 (MICH). BRITISH GUIANA. Yupukari, basin of Rupununi River, 15 Oct 1937 (imm fr). Smith 2274 (NY); Kanuku Mountains, drainage of Takutu River, elev 300 m. Mar 1938 (fr). Smith 3123 (NY, W ) ; Kaieteur Falls, Potaro River, Oct-Nov 1923 (bud), /. S. de la Cruz 4431 (MICH). SURINAME. Along Rijsdijkweg, Lelydorpplan, ca 25 km S of Paramaribo, 23 Apr 1954 (bud), Lindeman 5752 (MICH, U ) ; Jodensavanne- Mapane Creek area, Suriname River, 6 Oct 1953 (fr), Lindeman 4877 (MICH, U). BRAZIL. Para: "in vicinibus Santarem," Spruce 314 ["Myrcia (5)"] (CGE, isotype of ^. pruinosa); Santarem, 4 Apr 1943 (fr), Archer 8330 (MICH), 8 Apr 1943 (fr). Archer 8345 (MICH), 20 Nov 1960 (bud, imm fr), Pires 7678 (MICH); Monte Alegre, vicinity of Serra do Luna, 16 Sep 1953 (fl), Froes 30270, 30276 (both MICH); without locality, Martius (M, type of M. elegans; G-DC, fragment of same; Field Mus. neg. 19780). Amapa: Rio Oiapoque near Mt. Carupina, elev 10-80 m, 14 Oct 1960 (fl), Pires & Westra 48838 (MICH). Ceara or Piaui: Gardner 1621, 1625, 1626 (W, syntypes of A. gardneriana). The following specimens, all except one of which are from the lower Amazon, are probably referable to this variety. They resemble the type of Myrcia elegans DC. in being nearly or quite glabrous. The leaves are often obtuse and cuneate, rather than acuminate. Schultes' collection from the upper Rio Negro is put here with some hesitation; the leaves are all obtuse, cuneate or obovate, rather more coriaceous than specimens from the lower Amazon. BRAZIL. Amazonas: Rio Urubu, Maracarana, 23 Aug 1949 (fl), Froes 25115 (MICH); Manaus, km 19 on BR road 17, 15 Sep 1955 (imm fr), Rodrigues [INPA 1910] (MICH). Para: Rio Maro, afl. do R. Arapiuns, 22 Nov 1952 (fl), Pires & Silva 4384 (MICH); Entre Ilha do Anana e Igarape do campo coberto, Mpio. de Santarem, 28 Oct 1950 (bud). Black & Ledoux 10385 (MICH); Monte Alegre, 8 Sep 1953 (fl), Froes 30550 (MICH). COLOMBIA. Vaupes: Rio Negro, San Fehpe, below confluence of Rio Guainia and Rio Casiquiare, elev 180 m, 25 Oct 1952 (fl), Schultes et al 17999 (MICH). On the upper Amazon, the Rio Negro and its tributaries, and the upper Orinoco, the Myrcia guianensis-complex is represented by what seems to be a rather homogeneous population of plants that are glabrous or nearly glabrous, with leaves somewhat larger than those of the common plant of eastern South America, 5-9 cm long, 2.5-5 cm wide. The leaves on vigorous branchlets may be unusually broad for the species, as in the type-collection of Aulomyrcia uaupensis {Spruce 2703, seen at BR); cf also Field Mus. neg. 36574, a photograph of an isotype of A. uaupensis, at P. In the type of M. spi.xiana {Martius s n, seen at M ) the leaves on vigorous branchlets are up to 7 cm long and 3-4 cm wide, whereas on other branchlets they are no more than 6 cm long and 2-2.5 cm wide (cf Field Mus. neg. 19866). Except in these respects, I do not find any consistent differences between these plants and those of the lower Amazon. COLOMBIA. Vaupes: Rio Kuduyari, tributary of Rio Vaupes, elev ca 300 m, Apr 1953 (bud), Schultes & Cabrera 20038 (MICH). COLOMBIA (?). Panure, on Rio Vaupes, Spruce 2703 (BR, type of Aulomyrcia uaupensis; P, isotype; Field Mus. neg. 36574, photo of isotype at P). VENEZUELA. Amazonas: Upper Orinoco, Esmeralda, elev 130 m, 14 May 1942 (bud, imm fr), LI. Williams 15355 (F); Sanariapo, elev 124 m, 2 Jul 1942 (sterile), Williams 15964 (F). BRAZIL. "Prov. Sohmoes," Martius (M, type of M. spixiana; Field Mus. neg. 19866).