Correcting Errors Perpetuated in the Literature
Despite efforts to achieve accuracy, several facts regarding the discovery, distribution, and characteristics of the substrate in which Darlingtoniagrows have been misstated then repeated in the literature. This paper will discuss some of the mistakes encountered in the literature regarding Darlingtonia californica. The elevation, slope, calcium and magnesium levels of the water samples, and the pH of the water in which Darlingtonia was found growing on Mt. Eddy, California will be provided.
Darlingtonia californica is a well-known insectivorous pitcher plant belonging to the American pitcher plant family, Sarraceniaceae. It was first collected by William Brackenridge during the overland portion of the U.S. Exploring Expedition in early October, 1841. The three genera in this family have a wide geographic distribution: Sarracenia occur in the eastern United States; Heliamphora are found in northern South America; and Darlingtonia, a monotypic genus, grows in wet areas in western Oregon and northern California.
The most captivating feature of Darlingtonia is its pitcher, hence the common name, California Pitcher Plant. This modified leaf is composed of a twisted tube which enlarges into an inflated head that bends down like a hood. Near the opening on the underside of the hood is a forked appendage often referred to as a "fishtail appendage." The cobra-like shape of the pitcher and its fang-like appendage suggest its other common name, Cobra Lily.
Both the collector's name and date concerning the discovery of Darlingtonia have been incorrectly stated in the literature (Torrey 1853; Lloyd 1942; Schnell 1976; Slack 1979; Juniper et. al. 1989). This is due, in part, to John Torrey's 1853 article in Smithsonian Contributions to Knowledge. Torrey writes, "This new Pitcher-plant was first detected by Mr. J. D. [sic] Brackenridge...in the year 1842 [sic]." The errors relating to William D. Brackenridge's name and the date of discovery are most likely due to transcription or typographical errors. Now that these mistakes have entered the scientific literature, they are often accepted as facts.
A chased-by-Indians story is often associated with the discovery of Darlingtonia, apparently to explain the reason for the less-than-ideal quality of the specimen collected (Schnell 1976; Mellichamp 1983; Juniper, et. al. 1989, Rondeau 1991). This story has it that Brackenridge was unable to make a decent collection of Darlingtonia due to the "fact" that he was being pursued by Indians at the time. Eastwood (1945) and Maloney (1945) wrote articles that accompanied the first publication of Brackenridge's journal. Eastwood questioned the validity of this story and challenged anyone to provide evidence of the Indian-pursuit story related to the discovery of Darlingtonia. Eastwood finally found the story in print in The Life of James Dwight Dana by Daniel Coit Gilman (1899). Maloney figured Dana, who was on the expedition with Brackenridge, told the story to Gilman and considered the problem solved. However, Miesse (1993) points out that Gilman did not credit Dana with the story. Gilman may have had access to information which supported this story but he did not supply evidence of this in his account. Further, Brackenridge himself did not include any reference to this incident in his journal. The perpetuation of this story in the literature appears to be a literary device rather than an historical fact.
Literature pertaining to the distribution of Darlingtonia contains small errors which are mostly due to the age of the source consulted and the language style used. Over time, there has been an increase in knowledge of plant sites as herbarium collections have been made. Darlingtonia's distribution has become better known as specimens from several herbaria are studied as a group (e.g. De Buhr 1973). Articles that describe the distribution of Darlingtonia based on early sources may be incorrect in light of new evidence. Minor errors can also result when authors use directional or geographical designations that, if taken literally, do not describe the intended distribution accurately. For example, Cheatham (1976) states that Darlingtonia has a "...limited distribution to scattered locations in northern California and the southern half of Oregon." It would be more accurate to state that Darlingtonia grows in western Oregon, rather than southern Oregon, as it is not found in southeastern Oregon and it is found in northwestern Oregon in Linn, Tillamook, and Lincoln counties (DeBuhr 1973).
The upper and lower elevational limits of Darlingtonia differ slightly among various sources. The range in elevation is approximately sea level to about 2600 meters. Schnell (1976) and others list the range as sea level to 2800 meters. The highest peak in Darlingtonia's known geographic range is Mt. Eddy (2751 meters) and the next highest peak is Mt. Thompson in the Trinity Alps (2741 meters). Not only are both peaks less than 2800 meters, but Darlingtonia needs water from runoff and therefore will not be found growing on the peaks themselves. The highest elevation at which Darlingtonia is found on Mt. Eddy is 2390 meters, but it was most commonly found between 1700 and 2100 meters (Freeman 1994). The highest it has been recorded growing in the southern Klamath Ranges is 2587 meters (Rondeau 1991).
An early study of Darlingtonia by Mary Austin (Juniper et. al. 1989) suggested that Darlingtonia was confined to south- and southwest-facing slopes. While Darlingtonia may, in fact, have been limited to these slopes in the earlier study, that is no reason to believe that Darlingtonia is confined to south- and southwest-facing slopes throughout its range. Darlingtonia was found growing on virtually all slope aspects on Mt. Eddy, indicating that there are no apparent slope-orientation requirements for the California Pitcher Plant.
Differences of opinion exist regarding the pH of the substrate in which Darlingtonia grows. Part of the confusion stems from the fact that Darlingtonia grows in wet areas, which are often referred to as bogs. Since bogs are commonly thought to be acidic, the inference has been made that Darlingtonia grows in an acidic medium (e.g. Naeem and Dusheck 1985; Schoenherr 1992). However, the marshy areas in which Darlingtonia is found growing are more accurately called seeps (Sawyer 1986); using this term could prevent one from concluding that the water is acidic. Many sources (DeBuhr 1973; Cheatham 1976; Schnell 1976; Naeem and Dusheck 1985; Sawyer 1986; Juniper, et. al. 1989; Schoenherr 1992) point out the association of Darlingtonia with serpentine or ultramafic soils, which tend to produce alkaline runoff. Only two of the cited studies (Rondeau 1991; Juniper, et. al. 1989) actually give the pH values (5.1- 7.0 and 7.5-9.5 respectively). It appears that the pH of the water or soil in which Darlingtonia grows has not been tested throughout its range. In the study area Darlingtonia is more commonly found in association with water having a pH from 7 to 8 but it grows in both acidic and basic waters, with the pH ranging from 5.2 to 8.5.
The substrate in which Darlingtonia grows needs further study. Several articles (Cheatham 1976; Schnell 1976; Mellichamp 1983; Naeem and Dusheck 1985) state that the California Pitcher Plant grows in a nutrient-deficient medium, but they do not provide evidence which supports this claim. Many sources (Cheatham 1976; Mellichamp 1983; Naeem and Dusheck 1985) imply that the soil or water where Darlingtonia grows is high in magnesium, nickel, and chromium, but values for these metals are often not given nor is the term "high" defined. The magnesium levels of the water samples from the study area ranged from 44 mg/l to 223 mg/l while the calcium levels ranged from 2 mg/l to 18 mg/l. The average concentration of calcium in river water is 13.4 to15 mg/l and the average concentration of magnesium is 3.35 to 4.1 (Hem, 1989). Since magnesium hinders calcium absorption by plants, these data add support to statements made in the literature regarding the "poor" quality of the substrate in which Darlingtonia grows, but they do not verify these statements.
Regardless of the minor errors, the literature pertaining to Darlingtonia is interesting and informative; however, this unusual plant needs further research. As the distribution and habitat of Darlingtonia become more thoroughly documented throughout its range, biogeographers will be better able to explain the reasons for its distribution patterns.
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