Harlan Lewis

Terpenes as taxonomic characters in Salvia section Audibertia

A survey of terpene differences in the 19 species ofSalvia indigenous to California and Baja California suggests that identification of species is possible solely on the characteristic composition of terpenes. Further, differences between two introgressing species (5.apiana and 5.mellifera) are such that terpenes may be treated as characters from which hybrid indices and histograms may be formulated. Statistical comparison of these data with those from morphology shows a highly significant correlation.

The genus gayophytum (Onagraceae)

Gayophytum comprises a small homogeneous group of species endemic to western North and South America. The species have been variously delimited (e.g., Munz 1932, 1959; Jepson 1936), suggesting that the group is inherently complex. We have attempted, therefore, to obtain a better understanding of it using chromosome cytology, breeding habit, and ecogeographic distribution, together with morphology, but without growing experimental progenies or making hybrids. Our genetic interpretations are extrapolations from the extensive experimental work on closely related groups. The present study had an auspicious beginning. The first population examined consisted of plants with all of the chromosomes joined into a ring at meiosis (as in some species of Oenothera), whereas a morphologically similar population adjacent to it was tetraploid. Furthermore, both were autogamous. In examining these two populations we had found what proved to have been the cause of much of the earlier difficulty of interpreting the group: polyploidy, autogamy, and complex heterozygosity. The initial study was begun while the senior author was a Guggenheim Fellow working at the Carnegie Institution of Washington field station at Mather, and has been continued with support from the National Science Foundation. Studies in Jackson Hole, Wyoming, were made through the courtesy of the Biological Research Station of the University of Wyoming. The junior author worked on this project while he held a Rockefeller Foundation Fellowship. We are very grateful for this support and cooperation. We are also greatly indebted to Susan J. Ahrend for the drawings in Fig. 5 (except E and H) ; to Albert Hill and Marcella Juhren for aid in the preparation of the other illustrations; to Kunjamma Mathew for help with pollen counts; to David Bates for examining and photographing material at Paris and for bibliographical assistance; to W. S. Davis for assistance in plotting distributions; and to Kenton Chambers, Carl Epling, Clare Hardham, Donald Kyhos, Margaret Lewis, R. M. Mallory, David Moore, Theodore Mosquin, Philip Munz, Robert Ornduff, Peter Raven, Otto Solbrig, Richard Snow, William Theobald, Ernest Twisselmann, and H. L. Wedberg for collecting materials for us. We also wish to express our appreciation to the curators of the many herbaria who have kindly loaned us their collections.

The relationship of clarkias from two continents

SummaryFirst and second generation hybrids that have been obtained between the tetraploid speciesClarkia tenella andC. davyi suggest a very close relationship between the two.C. tenella is a species of south-western South America, whereasC. davyi is restricted to the sea-coast of central and northern California. The two are morphologically similar and chromosome pairing in their hybrid indicates a high degree of homology. The hybrids are nevertheless highly sterile. In view of the cytological and morphological similarity ofC. tenella andC. davyi, and taking into account their relation to other species of the sectionGodetia, their origin from a common segmental allotetraploid ancestor in North America is postulated. The conditions permitting rapid evolution ofClarkia into various xeric habitats which became available as a result of climatic changes in late Cenozoic time probably also permitted the successful introduction of the tetraploid ancestor ofC. tenella and of various other herbaceous species into South America by long-distance dispersal in late Pliocene or more recent time.

Clarkia franciscana, a new species from Central California

questionable one of 128 for Piper ~rigrt,m For one species of Piper haploid numbers of 8, 12, and 20 have been reported by different observers. One thus finds that the Piperaceae, though of little economic importance, exhibit features of great interest to the systematist, the anatomist, the cytologist, the ecologist, and even the sociologist. I t is certainly a family that merits expanded research.

Chromosome numbers and phylogeny of Trichostema

T.ITERATURE CITED Clausen, Jens. 1951. Stages in the evolution of plant species, viii-{-206 pp. Ithaca, Cornell University Press. Darlington, Josephine. 1934. A monograph of the genus Mentzelia. Ann. Mo. Bot. Gard. 21: 103-226. Kellogg, A.. 1876. On some new species of California plants. Prec. Calif. Aead. Sei. I, 7: 110. l~unz, P. A., & Keck, D. 1949. California plant communities. Aliso 2: 87-105. Stebbins, G. L. 1957. The hybrid origin of mierospecies in the Elymus glauc,~ts complex. Proc. Intern. Genetics Symposia 1956: 336-340. (Supplement volume of Cytologia). Thompson, H. J. & :Lewis, H. 1955. Chronlosome numbers in Mentzelia (Loasaeeae). Madrofio 13: 102-107. Wolf, C. B. 1938. A revision of Mentzel~a lindleyi. Oce. Papers Rancho Santa Ann Bot. Gard. 1: 69-73.

Three Species Pairs from Southern and Lower California

The two principal and characteristic climax formations of coastal southern California and adjacent Lower California are the chaparral and coastal sage. Their distributional relationship suggests for both a similar historical development. The occurrence within each formation of several species pairs, one member of which has a more northerly distribution, usually in California, the other a more southerly distribution, usually in northwestern Lower California, suggests either that there have been two centers of speciation within these formations or that during their development a segregation of closely related forms has taken place. The purpose of this paper is to describe three of these pairs. The members of two pairs have long been recognized in the manuals as varietally different, but have never been clearly differentiated; one member of the third pair has only recently been discovered.