Camissonia

• Authority

  Raven, Peter H. 1969. A revision of the genus Camissonia (Onagraceae). Contr. U. S. Natl. Herb. 37: 161-396.

• Family

  Onagraceae

• Scientific Name

  Camissonia

• Type

  Type species: Camissonia dentata (Cav.) Reiche.

• Description

  
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  Description - Annuals, the plants caulescent, with no well-defined basal rosette, but the leaves sometimes clustered near the base, plants not flowering from the base. Leaves narrow, subsessile. Inflorescence nodding at anthesis, becoming erect in fruit. Flowers opening near sunrise. Ovary lacking a sterile projection. Sepals reflexed singly or in pairs. Petals yellow, often with one to several red dots near the base, fading reddish, with no contrasting pattern visible in ultraviolet light. Stamens, style, and inside of hypanthium yellow, the stigma yellow or greenish yellow. Capsule regularly loculicidal, straight or somewhat flexuous, subterete, more or less torulose, the seeds in one row in each locule, the friable central column much distorted by the seeds at maturity. Seeds with a scar at the micropylar end, blunt at the chalazal end, shining, dark brown, minutely lacunose, narrowly obovoid, more or less triangular in transection.

• Discussion

  Section VI. Camissonia sect. Camissonia is a close-knit group divided herein into 12 species with 4 additional subspecies. Two of these, C. kernensis and C. campestris, are self-incompatible diploids; two others, C. pusilla and C. sierrae, are self-compatible diploids; one is an autogamous hexaploid; and the remaining seven are autogamous tetraploids. One obviously closely interrelated group of species comprise the self-incompatible diploid C. kernensis, the autogamous diploid C. pusilla, and the two autogamous tetraploids C. pubens and C. parvula. These species differ from the others in their Great Basin habitat, and in having the sepals separating from one another when the flowers open. In the remaining species the sepals remain united in pairs. Relationships within this group are close, and the populations included here have generally been regarded as comprising only two species, the self-incompatible C campestris (usually known, incorrectly, as Oenothera dentata) and the autogamous C. contorta (usually divided into Oenothera contorta var. typica and O. contorta var. strigulosa). The species that I have named C. sierrae, C. benitensis, and C. integrifolia have hitherto been too poorly represented in collections to attract attention; C. lacustris has been confused with C. campestris and C. contorta (sens, lat.); and the extremely closely related trio consisting of the tetraploid C. strigulosa, the hexaploid C. contorta, and the South American tetraploid C. dentata (some populations with n=13, the only instance of aneuploidy known in the genus) has in North America been regarded as comprising Oenothera contorta var. strigulosa, var. epilobioides, and var. contorta, the lines between these taxa not corresponding to those between the species recognized here. These might all conservatively be treated as C. dentata sens, lat,, but I prefer to keep them separate for reasons that will be discussed in some detail below. Camissonia kernensis subsp. kernensis was initially attributed to Oenothera subg. Chylismia, but I excluded it from that group in 1962 (Univ. Calif. Publ. Bot. 34: 115). On the other hand, C. kernensis subsp. gilmanii was first described as a variety of C. campestris ("Oenothera dentata"); I pointed out the conspecificity of the two taxa here grouped as C. kernensis to Dr. Munz in 1963, and he brought them together in 1965 (N. Amer. Fl. II. 5: 158-159). Part of what is here regarded as C. kernensis subsp. gilmanii was included by Munz (Bot. Gaz. 85: 259. 1928) in his concept of Oenothera dentata var. ohnstonii, the type of which is Camissonia campestris. In the same 1928 treatment, Munz included all of the autogamous entities in this group in Oenothera contorta, with his var. pubens corresponding to C. pubens, his var. flexuosa to C. pusilla and C. parvula, his var. typica to much of C. contorta, and his var. epilobioides and var. strigulosa including the other autogamous taxa known to him. Determinations of chromosome number, and in many cases pairing, have been made of 177 individuals from 166 populations of this section, including a few counts reported earlier by Lewis, Raven, Venkatesh, & Wedberg (Aliso 4: 73-86. 1958) and two reported by Gregory & Klein (Aliso 4: 505-521. 1960). The chromosome number for Camissonia campestris (as Sphaerostigma dentatum and var. campestre) was reported by Johansen (Proc. Nat. Acad. Sci. U.S. 15: 884. 1929; Amer. Journ. Bot. 16: 597. 1929), but without any indication of voucher specimens. As far as I know, these are all of the available reports for the section. The degree of chromosomal structural heterozygosity in this section is low: of the 35 individuals of Camissonia campestris subsp. campestris examined, 3 had a ring of 4 chromosomes and 5 pairs and 1 had a chain of 3 plus a univalent and 5 pairs. Considering the two selfincompatible species in the section, C. campestris and C. kernensis, 49 individuals have been examined chromosomally, with the 4 just indicated being the only ones that were heterozygous—approximately 2 percent of the total. This is much lower than the more than 20 percent of 676 individuals of sect. Chylismia that were heterozygous for at least one reciprocal translocation, but significantly higher than in sect. Holostigma, where reciprocal translocations appear to play no role whatever in natural populations. Several interploid natural hybrids, discussed in the following pages, shed light on the pattern of chromosomal evolution in sect. Camissonia. For example, in hybrids between the diploid (n=7) C. campestris subsp. campestris and the hexaploid (n-=21) C. contorta, the maximum association of chromosomes observed was a chain of 8 chromosomes, a ring of 4, 2 chains of 4, 2 ring bivalents, and 2 rod bivalents. It is therefore obvious that the complete absence of multivalent configurations in the hexaploid is genetically controlled, and does not reflect any great degree of differentiation between the three genomes present in this species. No multivalents have been found in any polyploid in this section, and it would appear that even if the two diploid genomes present in a tetraploid would, on the basis of their homology, pair completely, they are prevented from doing this genetically. Natural hybrids between the tetraploids C. integrifolia and C. strigulosa, with up to 10 bivalents, and artificial hybrids between the North American tetraploid C. strigulosa and the South American tetraploid O. dentata, which show few multivalent associations despite their high degree of sterility, tend to support this hypothesis (Raven & Moore, MS.). In sect, Camissonia, therefore, it appears that diploid genomes may be brought together in any way that will produce highly fit combinations for particular ecological situations, and that these polyploids will soon (perhaps initially) be pair-forming and highly fertile regardless of the degree of chromosomal divergence between their diploid antecedents. There appears to be a wide gap between the group of species consisting of C. kernensis, C. pusilla, C. pubens, and C. parvula, and the other species of the section; none of the polyploids appears to bridge the gap between these two groups. The synonymous name Onothera torulosa H. Lev., Monogr. Onoth. 176. 1905, requires special mention here; this name was an illegitimate substitute for most of the species in this section published earlier, and it is not practical to cite it in the synonymy of all of these names or to attempt to typify it by one of these concepts; as far as I know, the concept has never been taken up by any author other than Léveillé.