Cojoba beckii
Rupert C. Barneby
4. Cojoba beckii Barneby & Grimes, sp. nov., ab aliis congeneribus austroamericanis omnibus foliorum formula foliolorumque amplitudine (pinnis 1-2-jugis, foliolis 6-8-jugis et fere 2-3 cm usque latis) primo intuitu distincta. — BOLIVIA. La Paz, Nord-Yungas: Caranavi, 12 km hacia Coroico, 16.IX. 1981 (fl), S. G. Beck 4860. — Holotypus, NY.— Ibid., cataracts of Río Bopi, 2.VIII. 1921 (fl), H. H. Rusby 702. — Paratypi, GH, NY, US.
Amply leafy trees to 20 m tall with smooth gray bark, the young branches, lf-stks, dorsal face of lf-axes and peduncles puberulent with fine yellowish gray hairs to 0.15-0.3 mm, the lf-buds brown-tomentulose, the thin-textured lfts bicolored, dark green above, paler beneath, either glabrous throughout, or glabrous ciliolate, or minutely puberulent along some primary veins, the dense globose capitula of greenish tubular fls fasciculate (solitary) and arising sequentially in lf-axils either of annotinous branches below the homotinous lvs or some in axil of coeval lvs, then fully immersed in foliage. Stipules minute, 0.5(—?) mm, caducous. Lf-formula i-ii/6-8; lf-stks 3.5-8 cm, the petiole 3.5-5 cm, the 1 interpinnal segment, when present, 2-2.5 cm; a sessile round nectary <0.7 mm diam between or shortly below each pinna-pair and similar but smaller ones on pinna-rachis near 1-4 furthest pairs of lfts; rachises of one or further pinna-pair 8-15 cm, the ventrally keeled interfoliolar segments 12-25 mm; minute caducous paraphyllidia at top of each pinna-pulvinus; lft-pulvinules subcontiguous on ventral side of rachis, 1-1.5 x 1.2-1.8 mm, transversely wrinkled; lfts distally accrescent, the blades obtusely rhombic- to oblong-elliptic from inequilateral base, broadly shallowly emarginate, the distal pair 3-6 x 2-3.2 cm, 1.5-2.3 times as long as wide; venation palmate and pinnate, the finely prominulous, straight or slightly recurved midrib a little forwardly displaced, the 2-5 posterior ones weaker, the inner faintly brochidodrome near or short of midblade, all repeatedly branching into a fine reticulum prominulous on both faces. Peduncles (1—)2—5 per node, 5.5-10 cm, charged above middle with a small ventrally concave bract; capitula 50-80- fld, the sessile fls spreading in all directions from the globose receptacle, homomorphic; bracts spatulate, 1 mm or less, caducous; perianth 5-merous, glabrous except for brown-puberulent calyx-teeth and tip of corolla-lobes; calyx campanulate 1.4-2.6 x 0.9-1.1 mm, the depressed-deltate teeth 0.1-0.2 mm; corolla tubular, slightly dilated distally, 7.2-9.7 mm, the erect ovate lobes 0.4-0.9 mm; androecium 32-46-merous, 13-16.5 mm, the stemonozone <1 mm, the tube 7-9 mm; ovary sessile, linear-ellipsoid, glabrous, style a little exserted. Fruit unknown.
In forest, sometimes on river banks, near 900 m, on E slope of the Bolivian Andes in Nor-Yungas near 16°10'-35'S (Coroico, Río Bopi). — Map 16. — Fl. VIII-XI.
Cojoba beckii is most closely related to C. chazutensis (Fig. 3). However, until the fruit is known there will remain a trace of doubt as to the generic position of C. beckii, but its spherical capitula of narrow tubular flowers and the general aspect of its foliage and inflorescence appear to us decisive. The relatively few and ample leaflets distinguish C. beckii abruptly from allopatric C. chazutensis, and even further from C. arborea var. angustifolia, which occurs also in the Yungas.
Cojoba beckii was collected first by Rusby in 1921. It is named in honor of Dr. Stephan G. Beck of the National Herbarium at La Paz, whose collections of Bolivian Leguminosae have greatly enriched the herbarium at NY.
References: [Article] Barneby, Rupert C. & Grimes, James W. 1997. Silk tree, guanacaste, monkey's earring: A generic system for the synandrous Mimosaceae of the Americas. Part II.