Penstemon cardwelliiPenstemon deustusPenstemon venustus

P. cardwellii

P. deustus

P. venustus

Bibliography and Suggested Readings

Arekal, G. D. 1963. Contribution to the embryology of Chelone glabra L. Phytomorphology 376-388.

Baker, H. G. 1963. Evolutionary mechanisms in pollination biology. Science 139: 877-883.

Banerji, I. 1961. The endosperm of Scrophulariaceae. The Journal of the Indian Botanical Society XL: 1-11.

Bellini, d. R. 1907. Criteri per una nuova classificazione delle Personatae. Annali de Botanica 6: 131-145.

Bennett, R. W. 1960. Penstemon nomenclature. Bulletin of the American Penstemon Society 19: 115-165.

Bennett, R. W. 1963. Notes on eastern North American species of Penstemon. Phytologia 9: 57-58.

Bennett, R. W. and D. D. Keck. 1953. Chart of the subdivisions, species, and subspecies of Penstemon. 78-85.

Bennett, R. W., K. Lodewick, and R. Lodewick. 1987. Penstemon nomenclature. Eugene, OR: American Penstemon Society.

Bigazzi, M. 1993. A survey on the intranuclear inclusions in the Scrophulariaceae and their systematic significance. Nordic Journal of Botany 13: 19-31.

Burtt, B. L. 1965. The transfer of Cyrtandromoea from Gesneriaceae to Scrophulariaceae, with notes on the classification of that family. Bulletin of the Botanical Survey of India 7: 73-88.

Campbell, D. H. 1930. The relationships of Paulownia. Bulletin of the Torrey Botanical Club 57: 47-50.

Clausen, J. 1933. Cytological evidence for the hybrid origin of Penstemon neotericus Keck. 5-76.

Clausen, J., D. D. Keck and W. M. Hiesey. 1940. Experimental studies on the nature of species. VII. Penstemon: A study in cytotaxonomy and transplanting. Carnegie Institution of Washington Publication No. 520 260-295.

Clokey, I. W. and D. D. Keck. 1939. Reconsideration of certain members of Penstemon subsection Spectabiles. Bulletin of the Southern California Academy of Sciences 38: 8-13.

Cooperrider, T. S. 1976. Notes on Ohio Scrophulariaceae. Castanea 41: 223-226.

Cronquist, A. 1964. A new variety of Penstemon davidsonii from Nevada and Oregon. Leaflets of Western Botany X: 129-133.

Crosswhite, F. S. 1965. Concerning Penstemon unilateralis and Penstemon secundiflorus. The Southwestern Naturalist 10: 318.

Crosswhite, F. S. 1965. Hybridization of Penstemon barbatus (Scrophulariaceae) of section Elmigera with species of Habroanthus. The Southwestern Naturalist 10: 234-237.

Crosswhite, F. S. 1965. Published illustrations of Penstemon hirsutus (Scrophulariaceae): magnificance, malformation and misidentification. Sida 2: 157-159.

Crosswhite, F. S. 1965. Revision of Penstemon section Penstemon (Scrophulariaceae) II. A western alliance in series Graciles. The American Midland Naturalist 74: 429-442.

Crosswhite, F. S. 1965. Subdivisions of Penstemon section Penstemon. Sida 2: 160-162.

Crosswhite, F. S. 1966. Penstemon moronensis Crosswhite (Scrophulariaceae), a new species from Mexico (Zacatecas). SIDA 2: 266-267.

Crosswhite, F. S. 1966. Revision of Penstemon section Chamaeleon (Scrophulariaceae). Sida 2: 339-346.

Crosswhite, F. S. 1967. Against proliferation of superfluous names by giving formal status to spelling variants. Taxon 16: 109-112.

Crosswhite, F. S. 1967. Revision of Penstemon section Habroanthus (Scrophulariaceae) I: Conspectus. The American Midland Naturalist 77: 1-11.

Crosswhite, F. S. 1967. Revision of Penstemon section Habroanthus (Scrophulariaceae) II: Series Speciosi. The American Midland Naturalist 77: 12-27.

Crosswhite, F. S. 1967. Revision of Penstemon section Habroanthus (Scrophulariaceae) III: Series Virgati. The American Midland Naturalist 77: 28-41.

Crosswhite, F. S. 1970. Revision of Penstemon (Section Leptostemon) series Racemosi. The American Midland Naturalist 84: 237-243.

Crosswhite, F. S. and C. D. Crosswhite. 1966. Insect pollinators of Penstemon series Graciles (Scrophulariaceae) with notes on Osmia and other Megachilidae. The American Midland Naturalist 76: 450-467.

Crosswhite, F. S. and S. Kawano. 1965. Chromosome numbers in Penstemon (Scrophulariaceae) I: New mitotic counts. Rhodora 67: 187-190.

Danley, D. M. 1985. A new Penstemon (Scrophulariaceae) from northwestern Nevada. Brittonia 37: 321-324.

Everett, P. C. 1950. The California penstemons. Aliso 2: 155-198.

Grant, K. A. and V. Grant. 1968. Hummingbirds and their flowers. New York: Columbia University Press.

Grant, V. 1981. Plant speciation, 2d ed. Columbia University Press, New York.

Grant, V. 1994. Modes and origins of mechanical and ethological isolation in angiosperms. Proceedings of the National Academy of Sciences, U.S.A. 91: 3-10.

Keck, D. D. 1932. Studies in Penstemon: a systematic treatment of the section Saccanthera. University of California Publications in Botany 16: 367-426.

Keck, D. D. 1936. Studies in Penstemon II. The section Hesperothamnus. Madroņo 3: 200-219.

Keck, D. D. 1936. Studies in Penstemon III. The section Cryptostemon. Madroņo 3: 248-250.

Keck, D. D. 1937. Studies in Penstemon V. The section Peltanthera. American Midland Naturalist 18: 790-829.

Keck, D. D. 1938. Studies in Penstemon VI. The section Aurator. Bulletin of the Torrey Botanical Club 65: 233-255.

Keck, D. D. 1940. Studies in Penstemon VII. The subsections Gairdneriani, Deusti, and Arenarii of the Graciles, and miscellaneous new species. The American Midland Naturalist 23: 594-616.

Keck, D. D. 1945. Studies in Penstemon VIII. A cyto-taxonomic account of the section Spermunculus. American Midland Naturalist 33: 128-206.

Keck, D. D. and A. Cronquist. 1957. Studies in Penstemon IX. Notes on northwestern American Species. Brittonia 8: 247-250.

Lodewick, R. 1994. Descriptive key to Oregon penstemons. Kalmiopsis 1994: 12-22.

Meyer, S. E., S. G. Kitchen and S. L. Carlson. 1995. Seed germination timing patterns in Intermountain Penstemon (Scrophulariaceae). American Journal of Botany 82: 377-389.

Mitchell, R. J. 1988. Is Penstemon centranthifolius truly hummingbird pollinated? Crossosoma 15: 1-9.

Nisbet, G. T. and R. C. Jackson. 1960. The genus Penstemon in New Mexico. University of Kansas Science Bulletin 41: 691-759.

Pennell, F. W. 1935. The Scrophulariaceae of eastern temperate North America. Philadelphia, PA, Academy of Natural Sciences of Philadelphia.

Pennell, F. W. 1951. On the systematics of Penstemon. National Horticultural Magazine January, 1951: 8-15.

Stebbins, G. L. 1959. The role of hybridization in evolution. Proceedings of the American Philosophical Society 103: 231-251.

Stebbins, G. L. 1969. The significance of hybridization for plant taxonomy and evolution. Taxon 18: 26-35.

Straw, R. M. 1955. Hybridization, homogamy, and sympatric speciation. Evolution 9: 441-444.

Straw, R. M. 1956. Adaptive morphology of the Penstemon flower. Phytomorphology 6: 112-118.

Straw, R. M. 1956. Floral isolation in Penstemon. American Midland Naturalist 90: 47-53.

Straw, R. M. 1959. Los Penstemon de Mexico. Del Boletin de la Sociedad Botanica de Mexico 24: 39-52.

Straw, R. M. 1962. The Penstemons of Mexico. II. Penstemon hartwegii, Penstemon gentianoides, and their allies. Boletin de la Sociedad Botanica de Mexico 27: 1-25.

Straw, R. M. 1963. Bee-fly pollination of Penstemon ambiguus. Ecology 44: 818-819.

Straw, R. M. 1963. The penstemons of Mexico. III. Two subsections in the section Fasciculus. Brittonia 15: 49-64.

Straw, R. M. 1966. A redefinition of Penstemon (Scrophulariaceae). Brittonia 18: 80-95.

Straw, R. M. 1967. Keckiella: new name for Keckia Straw (Scrophulariaceae). Brittonia 19: 203-204.

Straw, R. M. 1976. A new species of Penstemon (Scrophulariaceae) from Mexico. Madroņo 23: 263-265.

Straw, R. M. 1984. Penstemon miniatus (Scrophulariaceae): new combinations. Brittonia 36: 67.

Viehmyer, G. 1958. Reversal of evolution in the genus Penstemon. American Naturalist 92: 129-137.

Wolfe, A. D. and W. J. Elisens. 1993. Diploid hybrid speciation in Penstemon revisited. American Journal of Botany 80: 1082-1094.

Wolfe, A. D. and W. J. Elisens. 1994. Nuclear ribosomal DNA restriction-site variation in Penstemon section Peltanthera (Scrophulariaceae): An evaluation of diploid hybrid speciation and evidence for introgression. American Journal of Botany 81: 1627-1635.

Wolfe, A. D. and W. J. Elisens. 1995. Evidence of chloroplast capture and pollen-mediated gene flow in Penstemon sect. Peltanthera (Scrophulariaceae). Systematic Botany 20: 395-412.

Wolfe, A. D., W. J. Elisens, L. E. Watson, and C. W. dePamphilis. 1997. Using restriction-site variation of PCR-amplified cpDNA genes for phylogenetic analysis of tribe Cheoneae. American Journal of Botany 84: 555-564.

Wolfe, A. D., Q.-Y. Xiang, and S. R. Kephart. 1998. Diploid hybrid speciation in Penstemon (Scrophulariaceae). Proceedings of the National Academy of Sciences, USA 95: 5112-5115.

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