VILLADIA ACUTA (CRASSULACEAE), A NEW SPECIES FROM SAN LUIS POTOSI, MEXICO

REID MORAN AND CHARLES H. UHL

Here & there


Abstract. V. acuta is distinctive in section VILLADIA in its long corolla tube, nearly equalling the segments, and is noteworthy also for its close-set narrowly acute leaves. In its slender pistils with long styles and its white corolla with acute outcurved segments, it approaches V. diffusa Rose, of Chiapas, and V. pringlei Rose, of Chihuahua and Durango. Leaves and sepals of V. diffusa are shorter and obtuse; V. pringlei dies nearly to the base after flowering and has a denser thyrse. The gametic chromosome number of V. acuta is n = 16, so far found in only one other collection, of probable V. pringlei.


Mexico is so rich in plant life that any specialist wandering the back roads, and especially new roads, can scarcely help finding new plants. In July 1962 Myron Kimnach, traveling with Fernando Medellín-Leal and Elwood Molseed, vis­ited Pico el Agujon, in southern San Luis Potosi, on the newly opened road to Mina el Refugio, Guanajuato. In pine-oak woodland just below the peak they found a new cycad, Ceratozamia zaragozae, named the next year by Medellín-Leal (1963). Without even trying, they found ten cacti and other succulents, including three new Crassulaceae: Pachyphytum kimnachii Moran, Sedum reptans Clausen, and the following new species of Villadia. We recollected these plants in July 1966. The villadia flowered at the Huntington Botanical Gardens and in Ithaca and San Diego.



Fig. 1. Flowers of Villadia acuta (M. & U. 13383). 15 November 1970, x 3.


Villadia acuta Moran and Uhl, spec. nov.


Suffrutex pauciramosus glaber 2-3 dm altus, foliis coarctatis patentibus subulatis acutis 1-2 cm longis 1.5-3 mm latis. Inflorescentia spicata thyrsoideave densa 3-10 cm alta 10-40-ramosa, ramis vulgo 1-flora-tis interdum 2-3-floratis. Sepala aequalia lanceolata acuta 3.5-4 mm longa. Corolla alba, tubo 3.5-4 mm longo, segmentis excurvatis acutissimis 3.5-5 mm lon­gis. Pistilla 5-6 mm alta angusta, stylis 1.5-2 mm lon­gis. Species in VILLADIA corollae tubo longo segmentis paene aequanti peculiaris et foliis coarctatis patentibusque acutissimis notabilis. V. diffusae Rose affinis quae foliis sepalisque brevioribus obtusisque autem differt et V. pringlei proxima quae autem caulibus post anthesin ad basim mareescentibus thyrsoque densiori dif­fert.



Fig. 2. Flowering plant of V. acuta (M & U. 13383}, 12 December 1970, x 0.4.


Glabrous perennial with flowering stems that die back only partway, leaving somewhat woody branching perennial stems to 15 cm or more high and 5 mm thick, with densely leafy sterile shoots 1-3 cm long below at flowering time, their leaves lanceolate, acute, 5-10 mm long, finely papillose at apex. Roots tuberous, clustered, to 2 cm long and 5 mm thick, the epidermis finely cross-striate. Flowering stems 1-3 dm tall, 3 mm thick below, very leafy, with as many as 15 leaves per cm and so with well over 100 below inflores­cence. Leaves spreading or somewhat arching downward, subulate, tapering to sharply acute apex, the lower ones 1-2 cm long, 1.5-3 mm wide and nearly as thick, slightly spurred, very slightly papillose at apex, those at midstem ca. 1 cm long. Inflorescence a dense spike or thyrse 3-10 cm high, 1-2 cm thick, with 10-40 branches that are mostly 1-flowered but some 2-3-flowered and on a few thyrses predominantly so, flowering mostly from base upward; bracts ca. 6 mm long and 1 mm wide, the sterile ones (where flowers fail to develop) ascending, the fertile ones deflexed; flowers sessile, each with 2 lateral bracteoles ca. 3 mm long and 1 mm wide. Calyx divided to base ca. 1 mm thick, the sepals ascending-spreading, distinct and spurred, equal or subequal, lanceolate, acute, 3.5-4 mm long, 1 mm wide, ventrally flattened below and convex above, dorsally rounded, the margins acute be­low, obtuse above. Corolla in bud ca. 7.5 mm long and 2.5 mm thick, white with yellowish green for ca. 2 mm at apex, pentagonal, with segments imbricate, at anthesis white, 5-8 mm wide, the tube 3.5-4 mm long, 3-3.5 mm wide, slightly narrowed upward, the segments out-curved to recurved, narrowly triangular-ovate, narrowly acute, 3.5-5 mm long, 1.5-2 mm wide at base, subdorsally mucronate. Filaments white, 5-6 mm long from corolla base but adnate to corolla and scarcely evident below, so in effect inserted at mouth of tube 4 mm above base, the epipetalous 1.25-1.75 mm long, 0.3-0.5 mm wide at base, the antesepalous 1.5-2 mm long, 0.5 mm wide, attached very slightly higher; anthers yel­low, oval, 0.6-0.7 mm long, 0.5 mm wide. Nectar glands light yellow, lightly dotted above with red, oblong-cuneate, obliquely truncate, ca. 0.7 mm high, 0.5 mm wide, and 0.25 mm thick. Gynoecium white, 5-6 mm high, 2.2-2.5 mm thick, the pistils erect, appressed, lightly connate by margins for 1.25 mm, tapering to styles 1.5-2 mm long, which are at first appressed but later separated; ovules ca. 30, ca. 0.4 x 0.15 mm. Follicles and seeds not seen. Chromosomes: n = 16.



Fig. 3. Flowering branches of V. acuta (Kimnach 296}, 12 December 1963, x 0.5.


TYPE COLLECTION: On mossy rocks with Pachyphytum, Pinguicula, Laelia, Ceratozamia, Mammillaria, Quercus macrophylla, Echeveria bifida, Manfreda, east slope of Pico el Agujón, Sierra de la Equiteria, ca. 30 km SW of Rioverde, San Luis Potosí, Mexico (?near 21°38'N, 100°07'W), 22 July 1962, Myron Kimnach 296, HBG 16386: holotype ex hort 15 March 1964, BH 372699; isotypes HNT, SD.


DISTRIBUTION: Known only from the type lo­cality; paratypes: 1,700 m, R. Moran & C. H. Uhl 13383, flowering in San Diego (CAS, MEXU, SD).


The new species with its spicate to thyrsoid inflorescence belongs to section VILLADIA, where it falls with those few having slender pistils with long styles and having rather large white flowers with acute corolla segments that are spreading to slightly reflexed at the tips. It thus seems most closely related to V. diffusa Rose, which grows at 1,800 to 2,500 m in the mountains of Chiapas, some 900 km to the southeast, and especially to V. pringlei Rose, which grows at 2,000 to 2,700 m in the mountains of Chihuahua and Durango, some 600 km to the northwest. It differs from both, and from all other members of section VIL­LADIA, in its long corolla tube, nearly equalling the segments; and the free part of the filaments is proportionally shorter. Also, the leaves are more crowded than in these two and more sharp­ly acute; and the sepals and corolla segments are sharply acute. Villadia diffusa is an often sprawl­ing plant; and the leaves and sepals are shorter and obtuse. Villadia pringlei is generally a lower plant, and its stems die nearly to the base after flowering; the leaves and sepals are acute to ob­tuse and sometimes wider; and the thyrse is often denser, its branches generally with more flowers, some lower branches in several collections with 6 or more.


The type collection of V. acuta has a gametic chromosome number of n = 16. This number has thus far been found in only one other col­lection of Villadia, probably referable to V. prin­glei but a greenhouse plant hard to reconcile with the wild specimens. We have no count for typical V. diffusa from Chiapas, but a related plant from Guerrero and Oaxaca has n = 14.


We are grateful to the curators at BH/CU, CAS/ DS, ROPA, SD, TEX, and US for the loan of their specimens and for other favors. And we thank Myron Kimnach for the plants, for infor­mation, and for a review of the manuscript.


Reference


Medellín-Leal. F. 1963. A new species of Ceratozamia from San Luis Potosí. Brittonia 15: 175-176, figs. 1-4.


© Cactus & Succulent Journal of America, 1991