Feature Flower:
Jewel Flower
(Streptanthus glandulosus)

by David Rogers
IMAGE: Figure 1 (fig1.jpg)

Figure 1. Streptanthus glandulosus as photographed at The Pinnacles National Monument, San Benito County. Copyright 2003 by Keir Morse.

STREPTANTHUS GLANDULOSUS Hooker
Jewel Flower
(a.k.a., Common, Bristly or Glandular Jewel Flower)

By David Rogers

The most striking feature of a Jewel Flower is the calyx, for it is comprised of four semi-glossy blackish-purple sepals, the upper three of which give the flower an inflated and jewel-like appearance. The genus name Streptanthus, however, refers to the corolla, for it is derived from the Greek words strepas, twisted, and anthos, flower, and refers to the backwardly curved and wavy-margined petals. Glandulosus refers to the callus-tipped teeth on the margins of the leaves of this species.

IMAGE: Figure 2 (fig2.jpg)

Figure 2. S. glandulosus. Copyright Br. Alfred Brousseau, Saint Mary's College.

The genus Streptanthus is noteworthy for a number of reasons. The genus is comprised of about forty species of the western United States and northern Mexico, and twenty four species plus eleven lesser taxa occur in California, of which thirty two are endemic to the California Floristic Province. Seventeen of these taxa are listed as rare and seven as uncommon in the Jepson Manual (Hickman, ed., 1993), and 26 taxa are listed in the California Native Plant Society's Inventory of Rare and Endangered Plants. Many of these taxa, especially those belonging to the subgenus Euclisia, such as the S. glandulosus complex, are to varying degrees restricted to outcrops of serpentine rock.

Streptanthus glandulosus is widely distributed in the California Coast Ranges, from Tehama and Mendocino counties to San Luis Obispo County, but its populations are scattered and are usually found in small groups, for the species is restricted to dry sites where the soil is exceptionally poor. Although it is commonly found growing on serpentine soils, S. glandulosus is not restricted to serpentine; all it takes for this species to find a niche is a dry and highly exposed site where the soil is poor, shallow, loose or rocky enough to be unfavorable to most forms of plant life. This species also occurs on non-serpentine talus slopes.

Throughout most of the range of S. glandulosus, from southern Monterey County northward, plants having flowers with blackish-purple sepals are by far the most common. Reported sites for S. glandulosus in the Santa Lucia Mountains of Monterey County include the Mount Toro area, along the Coast Ridge Road above Posts, at the Hastings Natural History Reservation, in the Cachagua area, on Pine Ridge, on Chews Ridge, along the Black Cone Trail, along the Horse Pasture Trail in the Horse Pasture, Tassajara Hot Springs near the springs, at the Landels-Hill Big Creek Reserve, along the Gamboa Trail below Cone Peak, near Nacimiento Camp, in the vicinity of Jolon, near Lion's Den Camp and in the San Carpóforo Creek area.

The Streptanthus glandulosus complex (section Pulchelli of subgenus Euclisia) is polymorphic (highly variable), and may include paleoendemics and neoendemics (old elements and relatively recently evolved elements), and the typical form of S. glandulosus may be the ancestral element. Genetic drift may have played a significant role in the evolution of the complex, for estimates of gene flow among the scattered populations of the taxa are generally lower than is theoretically needed to counteract the effects of genetic drift. It has also been demonstrated that infertility between populations increases with the distance that they are separated (Mayer, Soltis & Soltis, 1994).

As treated by Buck, Taylor & Kruckeberg in the Jepson Manual (1993), the Streptanthus glandulosus complex is comprised of three species, S. glandulosus, S. albidus and S. niger. S. glandulosus is divided into three subspecies, glandulosus, pulchellus and secundus. Subspecies pulchellus, Mount Tamalpias Jewel Flower, is found only in the vicinity of Mount Tamalpias in Marin County, while subspecies secundus, One-Sided Jewel Flower, is much more widely distributed in the counties north of San Francisco. S. albidus is divided into two subspecies, albidus and peramoenus. Subspecies albidus, Metcalf Canyon Jewel Flower, occurs only on serpentine in the western foothills of the Diablo Range between Morgan Hill and San Jose, and is listed as an endangered species by the federal government, while subspecies peramoenus, Uncommon Jewel Flower, is found in the Diablo Range in Contra Costa, Alameda and Santa Clara counties, and in the Santa Lucia Mountains of southern Monterey County (south of the Nacimiento-Fergusson Road) and northwestern San Luis Obispo County. S. niger, Tiburon Jewel Flower, a very rare species that is limited to serpentine outcrops on the Tiburon Peninsula in Marin County, is listed as an endangered species by both the federal and state governments.

At least two other taxa of the genus Streptanthus occur in the Santa Lucia Mountains. In the Los Burros Creek area there is an apparently undescribed taxon of S. morrisonii F. W. Hoffman (Buck, et. al., in the Jepson Manual, 1993; Matthews 1997), and S. tortuosus Kellogg, Mountain Jewel Flower, is scattered on the higher peaks and ridges. The Santa Lucia Mountains populations of S. toruosus are greatly separated from the nearest populations in the northern Coast Ranges and Sierra Nevada.

The type specimen of S. glandulosus was collected in the vicinity of Monterey by David Douglas (1798-1834), the well-known early botanical explorer of western North America and Hawaii. Monterey served as Douglas' base while 'botanizing' California from 1830 to 1832.

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Figure 3. Douglas and Hooker.

The species was first named and described by Sir William Jackson Hooker (1785-1865), who at that time was a professor of botany at the University of Glasgow, Scotland (later on, from 1841-1865, Hooker served as the director of the Royal Botanical Garden, Kew). The following image includes both the text and its opposing illustration as published in volume one of Hooker's Icones Plantarum (1837):

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Figure 4. Table 40 of volume one of Hooker's Icones Plantarum.

Jewel Flowers are erect annual herbs with simple or divaricately branched stems ranging from about 1 to 10 dm. (4-40") tall. At least the lower part of the plant is covered with bristly hairs. The basal leaves, which can be as much as 10 cm. long, are produced in rosettes, and are commonly shed by the time the plant reaches maturity. The basal leaves are narrowly lanceolate to narrowly oblanceolate in outline and pinnately toothed; the teeth are callus tipped. The alternate and lanceolate to linear cauline (stem) leaves, which become increasingly reduced in size upwards, are sessile with clasping bases, and have either toothed or entire margins. The terminal inflorescences (racemes) become increasingly elongating with age, and the flowers are about .8 to 1.2 cm. long. The calyx is comprised of four dark purple or purplish black sepals, and the corolla is comprised of four oblong-linear and backwardly curved petals. The petals, which are about 6 to 12 mm. long, are most commonly white along their crisped (wavy) margins and veined light to dark purple within. The upper petals are broader and more recurved than the lower petals. The stamens are arranged in three pairs; the upper two, which share a filament that is fused for about two thirds of its length, have sterile or nearly sterile anthers (i.e., that produce little if any pollen), while the lower pair and the (shorter) lateral pair have fertile anthers. The stigma is directly attached (or nearly so) to the apex of a superior ovary (an ovary that is situated above the other parts of the flower); and the narrowly linear and flattened fruits (siliques) are about 5 to 9 cm. long. The flattened and narrowly winged seeds are oblong-oval and about 2 to 2.5 mm. long. The flowering period Streptanthus glandulosus is from April to June.

The genus Streptanthus is a member of the Mustard Family (Brassicaceae or Cruciferae), which is comprised of about 300 genera and roughly 3,000 species. The family is best known for its numerous "cruciferous vegetables" or "cole-crops," such as broccoli, cauliflower, cabbage, kale, brussels-sprouts, radish, bokchoy, mustard greens and seeds, and so on.

References/Bibliography

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