Fruit ID #7

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Fruit Identification Photos #7

Fruits Of The Mustard Family

Mustard Family (Brassicaceae)

The typical fruit of the mustard family (Brassicaceae) is called a silique. Flowers of the mustard family typically have four petals, four sepals and six stamens. The former family name Cruciferae is derived from "crucifer" or cross, in reference to the cross formed by the four petals. The family name Brassicaceae is derived from the type genus Brassica. All plant family names are now derived from a "type genus" and end in the suffix "ceae." Slender, dry, dehiscent fruits of the mustard family superficially resemble legumes, except the mustard silique is composed of two carpels with a partition or septum down the center (i.e. between the two carpels or valves). [The legume fruit is composed of a single carpel and does not have the central partition or septum.] Examples of plants with siliques include the field mustard, turnip and cabbage (all species of Brassica), stock (Mathiola), wallflower (Erysimum) and London rocket (Sisymbrium). Another type of fruit in the mustard family is called a silicle. The silicle is a shortened (less elongated) version of a silique, including sweet alyssum (Lobularia), peppergrass (Lepidium) and shepherd's purse (Capsella). Some species in the mustard family are difficult to identify with taxonomic keys and require close examination of the siliques. [Note: As with legumes there are a exceptions to the typical form of siliques and silicles. For example, in wild radish (Raphanus) the silique does not split lengthwise, but instead it breaks transversely into several seed-bearing joints. In lace pod (Thysanocarpus) the silicles are indehiscent.] The illustrations below show a typical mustard with siliques and another species with silicles. These two illustrations are only identified by the numbers 3 and 4 because they are used as unknowns in "Botany of Spring Wildflowers" (Botany 110) offered during the spring semester at Palomar College.

A purple-flowered wallflower (Erysimum linifolium). This mat-forming or clumping (cespitose) perennial is native to Spain and Portugal. Is is sometimes cultivated in southern California gardens. A bright yellow-flowered species called western wallflower (E. capitatum ssp. capitatum) is native throughout the mountains of San Diego County. The inflorescence is called a raceme, with each flower attached to a short stalk (pedicel). As the blossoms age and the petals wither and fall away, the ovaries of older flowers enlarge into slender siliques (red arrow). The shape of the silique (flattened vs. rounded or terete) is crucial in identifying some species of mustards.

Note: The word wallflower typically refers to several species of mustards in the genus Erysimum in the mustard family (Brassicaceae). The term "wallflower" also refers to a socially challenged boy or girl who remains at the sidelines of a dance or social event. This condition is usually caused by an abnormal fear or inability to interact with members of the same or opposite sex. It may also be caused by a fear or inability to dance in front of a lot of people.

Close-up view of the flowers and siliques of the purple-flowered European wallflower (Erysimum linifolium). The flowers have four petals, four sepals and six stamens, typical of the mustard family (Brassicaceae). The orientation of the stigma lobes (red arrow) relative to valves of the silique is an important trait used to identify some species of mustards. [Stigma lobes situated over the valves vs. stigma lobes situated over the placentae or septum.]

Close-up view of the flowers and siliques of the yellow-flowered western wallflower (Erysimum capitatum ssp. capitatum). Several subspecies of this brightly colored biennial or short-lived perennial wallflower occur throughout mountainous regions of the western United States, including the mountains of San Diego County.

One interesting perennial wildflower of the mustard family (Brassicaceae) with peculiar, lyre-shaped silicles is called "lyre pod" (Lyrocarpa coulteri var. palmeri). Lyre pod is occasionally seen in rocky outcrops and desert canyons of San Diego County and adjacent Baja California, often found growing among clumps of other shrubs. It produces small seed pods (silicles) with the general shape of a lyre, a small, stringed, harp-like instrument used by ancient Greeks to accompany singers and reciters. Curiously enough, a lyre-shaped marking also occurs on the head of a seldom-seen snake that inhabits nearby rocky outcrops and hides during the day in deep crevices and under exfoliating granite slabs. The lyre snake is a rear-fanged snake with a venom that immobilizes small nocturnal lizards and rodents, and even bats when they are roosting. Unlike its deadly African relative, the boomslang, the lyre snake is not considered especially dangerous to people.

Lyre Pod (Lyrocarpa coulteri var. palmeri), an interesting wildflower of Anza-Borrego Desert State Park in San Diego County, California. Note the slender, twisted petals and lyre-shaped silicles. Lyre pod is native to rocky outcrops and desert canyons in San Diego County and adjacent Baja California, often found growing among clumps of other shrubs.

Jewel flower (Caulanthus heterophyllus var. heterophyllus), a common native mustard in recently burned areas of chaparral in San Diego County. The flowers of this species have narrow (strap-shaped) petals and a distinctive urn-shaped calyx. This genus and several related genera separate out in couplet 20 (Group 1) of the Jepson Manual key to the Brassicaceae.

Two additional desert wildflowers of the mustard family (Brassicaceae) are "spectacle pod" (Dithyrea californica) and "desert candle" (Caulanthus inflatus). Spectacle pod is a small wildflower with seed pods (double silicles) that resemble pairs of miniature eye glasses or spectacles. It commonly grows in sandy desert riverbeds and along roadsides of the Colorado Desert. Any discussion of unusual desert mustards would be incomplete without mentioning the striking "desert candle" (Caulanthus inflatus). This annual wildflower is named for its inflated, tapering stem which resembles a candle. Other desert species of Caulanthus, such as C. cooperi and C. hallii have main stems that are much more slender. The "candles" of C. inflatus occasionally appear in profusion during years with sufficient rainfall, often along roadsides in the Mojave Desert and westward into California's San Joaquin Valley.

Left: Spectacle pod (Dithyrea californica), a fairly common annual wildflower in sandy areas of the Colorado Desert. The small fruits (double silicles) resemble miniature eye glasses. Right: Desert candle (Caulanthus inflatus), an annual wildflower with inflated stems that often appears on open flats and among shrubs in the Mojave Desert of California.

Illustration Of A Mustard With Silques

Illustration Of A Mustard With Silicles

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