PSEUDOHYDROSME GABUNENSIS ENGL.

Transcription

1 PSEUDOHYDROSME GABUNENSIS ENGL. J. BOGNER Botanischer Garten, Miinchen, West Germany The genus Pseudohydrosme was described by Engler (1892) from incomplete material with two species native in Gabon: P. gabunensis Engl. and P. buettneri Engl. During my collecting trip to Gabon in the year 1973, I especially looked for these species and I scheduled my visit to coincide with the flowering time of the two aroids, but they are so rare that I only found two specimens of P. gabunensis. Although there is still much undisturbed forest in Gabon; these species have not been collected since the original types: P. gabunensis by H. Soyaux on 13 October 1881 and P. buettneri by BUtner in September I carefully looked for them and asked people from the Forest School at Cap Esterias, but they never have seen these aroids, a remarkable fact because they are big and very attractive and cannot be overlooked. Nevertheless, all my efforts resulted in finding only P. gabunensis, after 92 years. It was flowering without the leaf during my visit and the tubers brought back to Germany produced leaves later in cultivation. Now I can give nearly full description of P. gabunensis, but unfortunately I can say nothing more about P. buettneri than Engler (1891,1911) has already published. When I saw the flowering P. gabunensis, it was clear to me that the genus Pseudohydrosme is very closely related to Anchomanes Schott, which has a long peduncled inflorescence and an unilocular ovary. P. gabunensis has a bilocular ovary and a very short peduncle Figure 1: Pseudohydrosme gabunensis Engl. Holotype Soyaux 299 (B). The name on the left and right label is in Engler's handwriting. Courtesy of Botanischer Garten und Botanischer Museum Berlin Dahlem. with a very short spadix too; also its spathe is of different structure. P. gabunensis and Anchomanes have a spadix without any sterile flowers (only P. buettneri has an appendix with staminodes), a spiny peduncle and petiole as well as nearly identical leaves; in addition, their pollen grains are of the same type. Both have the typical divided leaf blades of the Dracontium type, but the apices of the lobes or leaflets are truncate and end in two side tips. 31

2 32 AROIDEANA [Vol. 4 Figures 2,3 and 4: Pseudohydrosme gabunensis, Leaf.

3 1981] BOGNER: PSEUDOHYDROSME 33 Figure 5: Pseudohydrosme gabunensis Engl. Inflorescence before anthesis in its natural habitat near Libreville, Station forestier Sibang (Bogner 665). Figure 6: Pseudohydrosme gabunensis Engl. Flowering specimen during anthesis (Bogner 664). The type specimen of P. ga b unensis lacks the upperst part of the spathe and is therefore incomplete. It is clear to me now why the type specimen has an incomplete spathe. The spathe is fornicate, but the lower involute funnel-shaped part of the spathe is of a very thick structure, whereas the upper part is very thin. It can be expected that the upper part dries up after anthesis and that the lower thick part is persistent during fructification, but the latter I have not observed. The leaf was hitherto unknown and now I can give a more complete description, although the fruits have not been observed yet. Pseudohydrosme gabunensis Engl., Bot. Jahrb. 15: 455, t. 15/16 (1892); in Engler and Prantl, Natiirl. Pflanzenfam. Nachtr. zu II-IV, 59 (1897); N. E. Brown, in Dyer, Flora trop. Africa 7: 161 (1901); Engler in Das Pflanzenreich IV. 23 C (Heft 48): 48, f. 19 A-G (1911); illustr. in Aroideana 2 (4): cover photo (1979). - P. gabonensis Dur. et Schinz, Consp. Flora Afr. 5: 475 (1895). Tuber 9-12 cm in diameter, light brown and somewhat ringleted, partly with buds; roots 5-8 mm thick, brownish yellow. Cataphylls 5-6, the first ones the shortest, more or less triangular, membranaceous, soon drying, cm long, at the base (1) cm wide, slightly reddish and a little spotted, the veins stronger colored. Petiole m long, below cm in diameter, spiny, spotted (more or less

4 34 AROIDEANA [Vol. 4 Figure 7 : Pseudohydrosme gabunensis Engl. Inflorescence during anthesis in its natural habitat near Libreville. Station forestier Sibang (Bogner 664). Figure 8: Pseudohydrosme gabunensis Engl. Flowering specimen after anthesis (Bogner 664.)

5 1981] BOGNER: PSEUDOHYDROSME 35 dark green olive and spotted with small yellowish white points); spines 1-2 mm long. Leaf blade divided in three main parts, each segment cm long; rhachis more or less reddish, round below and flattened on upper side, its margins prominent; venation reticulate, veins underneath reddish, otherwise dark green; leaflets (4) 8-23 cm long and (2) 3-7 (11) cm wide, upper surface dark green with a blue grey touch, more or less shiny, apex truncate ending in two (0.5) 1-3 cm long acuminate to caudate side tips; the lowest leaflets ovate and cuspidate, cm long and cm wide. Peduncle short, yellowish, (3) 5-9 cm long and cm in diameter, spiny, green or light purplish with greenish white roundish to elongate spots, spines 1-2 mm long and greenish white; cataphylls together with the inflorescence of the same size and color as those with the leaf. Spathe (30) cm long, below for a length of cm involute to a tube, fleshy and to 5 mm thick, above arched. over and thin, more or less membranaceous, broad-pointed, margin slightly undulate; spathe outside greenish yellow, above getting a slight purplish touch; veins very prominent; inside below in the center deep purple, in the middle going over in a purple especially the veins, above greenish yellow (mostly the margin parts). Spadix more or less sessile, cylindric, blunt, fertile to its apex, (6) cm long and (1.5) cm in diameter; female part (4) cm long; male part (3.5) cm long. Pistil ca. 5 mm high; ovary globular to ellipsoid, somewhat squeezed, 2-3 mm in diameter, yellowish-whitish, bilocular, seldom trilocular, with one ovule in each locule, fixed at the base of the Figure 9: Pseudohydrosme gabunensis Engl. Spadix, spathe partly opened (Bogner 664). middle septum and ascending; ovule anatropous, ellipsoid, ca. 0.7 mm long and ca. 0.4 mm in diameter, funiculus ca. 0.5 mm long; style short, mm long and ca. 1.5 mm in diameter, of the same color as the ovary; stigma bilobed, seldom trilobed, papillose, depressed in the center, ca. 2 mm in diameter, reddish brown to purple. Stamens free, ca. 4 mm high and rectangular in cross section, ca. 1.8 (2) x 1.2 mm, slightly angled, yellowish and at its top purple; thecae oblong, ca. 3 mm long and opening by an apical pore; connective capitate and rising above the thecae; pollen yellow and excuded in strings, pollen grain ellipsoid, inaperturate, JI x JI, exine slightly scabrous. Fruits unknown.

6 36 AROIDEANA [Vol. 4 Figure 10: Pseudohydrosme gabunensis Engl. Lower part of the spadix with female flowers (Bogner 664). Figure 11: Pseudohydrosme gabunensis Engl. Upper part of the spadix with male flowers, pollen grains exuded in strings (Bogner 664). Distribution: Gabon, Mundagebiet, Sibange-Farm, Wald am Maveilufer; unmittelbar aus Knolle in der Erde; am Maveli, 13. Okt. 1881, Soyaux 299 (B). Sibang, hinter der Station forestier; wachst im sandigen Lehmboden im Regenwald, sehr schattig, ca. 20 m, 29. Oktober 1973, Bogner 664 (K, M, US). Ecology: Pseudohydrosme gabunensis was found growing in the humus layer of a sandy loam in deep shade. Other plants found together are Anchomanes nigritianus Rendle, a very rare species first found in South Nigeria, of which I collected one specimen only at a distance of less than 100 m from the locality of P. gabunensis. Also very common were Anchomanes difformis (Bl.) Engl. and Amorphophallus maculatus N. E. Br., which grew nearby. Pseudohydrosme gabunensis flowers before the single leaf appears and I found it in flower in October, whereas Anchomanes normally flowers together with the leaf, but sometimes it can also flower just before the leaf appears or together with the young leaf. Pollination: I collected as pollinators two different flies and two different beetles of the following families: Diptera: Choridae, Sphaeroceridae and Coleoptera: Scaphidiidae, Staphylinidae. They are normally found on rotten organic matter. Literature Cited Engler A Botanische Jahrbticher 15: Engler, A Araceae-Lasioideae in A. Engler, Das Pflanzenreich IV, 23C (Heft 48) Leipzig: W. Engelmann.

7 1981] BOGNER: PSEUDOHYDROSME 37 Figure 12: A nchomanes difformis (B1.) Engl. Gabon, near Cap Esterias (Bogner 604).. - Acknowledgements: I would like to thank very much the Belgian J. Gavage and the German R. Boning, both teachers at the Forest School in Cap Esterias at this time, for all their help during my stay in Gabon; Dr. G. Scherer, Zoologische Staatssammlung, Mlinchen (BRD) for the determination of the insects and Dr. W. Barthlott, Institut fur Systematische Botanik und Pflanzengeo grap hie, Heidelberg (BRD) for the photographs of the pollen grains. Figure 13: A nchomanes nigritianus RendIe. Flower specimen (Bogner 662).