Twisselmannia californica, a new genus and species from Kings County, California, is described and illustrated. Its relationships to other mustard genera are discussed. To the foreign reader, the discovery of a new genus from the United States would seem rather unusual, especially for a family like the Brassicaceae (Cruciferae), which has recently been treated for North America in the outstanding monograph by Rollins (1993). Although most of the North American flora north of Mexico is well known, numerous discoveries continue to be made, and it is estimated that several hundred new taxa remain to be discovered and named from the United States alone (Ertter, in press; Milius, 1999). Hartman and Nelson (1998) indicated that 1197 new taxa of vascular plants, including five genera based entirely on newly described species, were discovered in the United States and Canada between 1975 and 1994. Of these, 91 taxa belong to the Brassicaceae, and 217 (ca. 18%) were discovered from California alone. Recent outstanding discoveries in the Brassicaceae from California include the new genus and species Sibaropsis hammittii S. Boyd & T. S. Ross (Boyd & Ross, 1997) and Arabis hirshbergiae S. Boyd (Boyd, 1998). The remarkable new discovery, hereafter known as Twisselmannia californica, is based on a single specimen collected in 1994 and was nearly passed over by its collector as the common weed Capsella bursa-pastoris (L.) Medikus (Andrew Sanders, pers. comm.). It was sent initially to Reed C. Rollins who for reasons of deteriorating health never had the time to study it. The specimen, along with many others left in Dr. Rollins's office after he died, were loaned to me in November 1998. Upon a casual look at the specimen, it was immediately evident that it does not belong to any known genus in the Brassicaceae. Critical further study, as well as a thorough checking of Schulz (1936) and all the major floras of the world, supported the fact that the plant is a native new species that belongs to an undescribed monotypic genus. The saltbush scrub habitat in which TI californica grows belongs to a private property of ca. 1700-acre parcel land in Kings County that is up for development into an instant city, an action that would have resulted in the total destruction of the habitat (Andrew Sanders, pers. comm.) and perhaps the extinction of the species. It was planned that I and several colleagues would look for T californica in late February 1999 before I formally described it. However, due to the drought this year in that part of California and because of the immediate need to protect the habitat in which it grows, it became necessary to publish a formal account without delay. The genus, anecdotally referred to as the Kings Gold, is named in honor of Ernest C. Twisselmann (1917-1972), rancher and tireless botanical explorer of the arid lands of south-central California, whose name is synonymous with floristic works on the Inner South Coast Ranges. His initial attempt to compile a simple list of the plants on the Twisselmann family ranches culminated in A flora of the Temblor Range and the neighboring part of the San Joaquin Valley, all potential habitat for additional populations of Twisselmannia. He subsequently authored A flora of Kern County, His floras (Twisselmann, 1956, 1967) continue to inspire several of the most enthusiastic floristicians in California. Although the opportunity to honor Ernest Twisselmann with his own genus could not be passed by, credit must also be given to the discover, Ed LaRue, whose keen-sighted recognition of this anomalous mustard resulted in the fortuitous collection of the sole specimen currently known. Twisselmannia Al-Shehbaz, gen. nov. TYPE: Twisselmannia californica Al-Shehbaz. Herba annua; folia caulina pinnatisecta; racemi ad apicem bracteati, valde elongati; sepala oblonga, nonsaccata; petala lutea; stamina 6, tetradynama; fructus obdeltoidei, valde compressi, puberuli, valvis in dimidio inferiore carinatis, laevibus et tenuiter coriaceis, in dimidio superiore rotundatis, tuberculato-rugosis et crasse coriaceis vel sublignosis; septum valde angustatum; semina 4-8, oblonga, nonmucilaginosa; cotyledones incumbentes. Herbs annual. Trichomes unicellular, eglandular, simple and minutely forked. Stems erect, few NovoN 9: 132-135. 1999. This content downloaded from 157.55.39.141 on Sun, 11 Dec 2016 04:52:47 UTC All use subject to http://about.jstor.org/terms r Missouri Botanical
Read full abstract