John R. Reeder

Notes on Mexican grasses III Buchlomimus, another dioecious genus

The type of Bouteloua nervata Swallen (A. S. Hitchcock 6734) was collected in 1910 near Pachuca, Hidalgo, at an elevation of 8000 feet. No other specimens are cited along with the original description (Swallen 1939), although C. G. Pringle had collected this species in the same state in 1904. The Pringle material (No. 13241), from dry mesas near Metepec Station at 8300 feet elevation, was originally identified as Bouteloua stolonifera Scribn., and distributed with printed labels bearing that name. The type of B. stolonifera (Pringle 3174), is a quite different species, however, and is known only from the states of Zacatecas and San Luis Potosl. Moreover, the senior authors have recently shown that it is dioecious, and it has been described as a distinct genus, Cyclostachya (Reeder & Reeder 1963). In connection with the study which resulted in the description of Cyclostachya, we also examined specimens of Pringle 13241 and Hitchcock 6734. Plants of these two collections are certainly conspecific and, in fact, are quite similar except that the latter are more mature. Careful study of the spikelets revealed that although pistils with large feathery stigmas were present in many of the florets, stamens were always abortive or altogether lacking. This evidence suggested strongly that Bouteloua nervata is dioecious, and that the material before us represented only the pistillate plants. Subsequent examination of additional specimens of Pringle 13241 from other herbaria only strengthened our convictions. All plants examined had florets with well-developed pistils, but stamens, when present at all, were always abortive. The type collection, Hitchcock 6734, is apparently represented by a single sheet in the United States National Herbarium. Since we could only guess at the appearance of the staminate plants, if they indeed did exist, it seemed advisable to withhold any announcement that we suspected the species to be dioecious until we had an opportunity to search for the staminate plants in the field. In this connection, a problem arose as to the time of year at which one might reasonably expect to find the species in flower; the label on the Hitchcock sheet indicated that the plants were collected in September, whereas Pringle had gathered his material in June! In September, 1963, in connection with attendance at the II Congreso Mexicano de Bot~nica, we were able to visit the mountains near Pachuca. As we approached the type locality of Bouteloua nervata, we were filled with apprehension. There were only two collections of this species, both of them made more than half a century ago. Perhaps the species had been very rare and was now extinct. Even if it did exist, what were the chances that we could find it in flower and thus be able to determine whether or not it was really dioecious? Driving across the mesa near Ixmiquilpan, we were discouraged to note the obvious dryness of the terrain. Except for some small plants of Muhlenbergia depauperata Scribn. growing in depressions, there seemed to be few grasses in proper condition to collect. As we began the ascent in the mountains east of Pachuca, through the extensive maguey fields, there

Calamovilfa, a misplaced genus of Gramineae

SummaryCalamovilfa, generally considered to be a member of the tribe Agrostideae and most closely allied to such genera asCalamagrostis andAmmophila, was investigated, using as criteria the embryo structure, lodicules, leaf epidermis and anatomy, and chromosome size and number. These studies revealed thatCalamovilfa belongs with the chloridoid-eragrostoid group, whereasAgrostis,Calamagrostis, andAmmophila, with which it was compared, are truly festucoid. All evidence indicates strongly thatCalamovilfa is most closely related toSporobolus. These two genera are not only very similar with respect to criteria mentioned above, but also on the basis of a number of gross morphological features, particularly those of the spikelet and the fruit.

The Status of Setaria macrostachya and its Relationship to S. vulpiseta (Gramineae)

Abstract Setaria macrostachya and S. vulpiseta have been treated as distinct species by most authors since they were first described more than 180 years ago. In three recent publications, however, S. macrostachya was listed as a synonym of S. vulpiseta. The present study, which included the examination of some 350 herbarium specimens, has convinced us that these two species are as distinct as many others in the genus, and should continue to be recognized as separate taxa. Communicating Editor: Jerrold Davis

Notes on Pappophorum (Gramineae: Pappophoreae)

The American genus Pappophorum, with species in both Northern and Southern hemi- spheres, has been a source of considerable taxonomic confusion. During the past two decades, various agrostologists have estimated the number of species to be from 9 to 20. Not only has there been disagreement regarding the number of species, the application of various binomials has differed among specialists who have studied the group. Three names that have continued to be applied in different senses are: P. mucronulatum, P. subbulbosum, and P. vaginatum Buckley, non Philippi. For many years the name P. mucronulatum was applied to plants from both North and South America, and P. subbulbosum and P. vaginatum were relegated to synonymy under that name. Some recent botanists have held that only P. pappiferum and perhaps P. subbulbosum are amphitropic, whereas P. vaginatum is restricted to North America, and P. mucronulatum and P. subbulbosum, both distinct species, occur only in South America. Authors of the present study recognize only eight species for the genus. Pappophorum mucronulatum is treated as a South American species, which is restricted to Brazil, Colombia, and Venezuela. Pappophorum vaginatum, with P. subbulbosum as a synonym, occurs in the southwestern United States and Mexico, and also in Argentina and Uruguay. A key to the species along with the important synonymy is provided. Pappophorum Schreber is an American genus, with the majority of taxa in the Southern Hemi- sphere. The range in South America is from Colombia and Venezuela, south through Ec- uador, Peru, Bolivia, and Brazil to Paraguay, Argentina, and Uruguay, and in North America from Mexico to southwestern U.S.A. Estimates regarding the total number of species have var- ied from 12 (Burkart 1969) to 20 (Cabrera 1970; Nicora 1978). Pensiero (1986), the most recent South American author to deal with Pappopho- rum, listed the number as approximately 10, which is in essential agreement with Clayton and Renvoize (1986), who gave the number as nine. Hitchcock (1913), in his treatment of the Mex- ican grasses, listed three species under Pappo- phorum. One of these, P. wrightii S. Watson, is a