Jepson Upgrade Key #1
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Jepson Upgrade Key #1: An Unknown Mustard

Silique: Two carpels separated by a seed-bearing septum.

The silique is an elongate fruit composed of two carpels separated by a seed-bearing partition. The silicle is very similar except it is much shorter (less than twice as long as broad). Siliques and silicles have parietal placentation. They are the characteristic fruits of the mustard family (Brassicaceae). Some members of the mustard family have siliques that do not split longitudinally into two separate carpels. For example, fruits of the radish (Raphanus sativus) split transversely into seed-bearing sections (joints).

In this species, the overlapping seeds are connected to alternate edges of the septum within each locule. The minute seeds are attached to both margins of the central septum. This revelation requires the skillful use of a dissecting microscope. In the Jepson Flora of California (1993), this genus keys out under "one row of seeds in each locule," without mentioning the alternating seed attachments along both edges of the septum. Apparently, the superficial appearance of the overlapping seeds in a single file is the defining character for the key.

This species was collected along the damp seepage area of a lawn in northern San Diego County. It is an annual with a fibrous root system (without rhizomes). The leafy stems are erect or ascending (curving upward from the base). The leaves are odd pinnate with 2 or three pairs of leaflets. A native species reported for San Diego County (C. oligosperma Torrey & A. Gray) has similar compound leaves; however, it has a distinct basal leaf rosette that is lacking in the above image. It is interesting to note that this species has now been added to the San Diego Natural History Museum on-line Checklist of Vascular Plants of San Diego County.

C. hirsuta L. from the San Diego Wild Animal Park. This weedy species is very similar to the native C. oligosperma, except it has only 4 stamens and more slender siliques (1 mm wide). C. oligosperma has 6 stamens (4 long and 2 short). Like C. flexuosa, its range in San Diego County appears to be increasing.

Revised Key In Jepson Manual: You Should Be On The Correct Page & Genus:

1. Lvs. simple, shallowly lobed to gen entire

1' Lvs or at least lower cauline palmately or pinnately lobed to compound

  5. St widened to strong attachment with rhizome or rhizome 0

  5' St narrowed to weak attachment with rhizome; rhizome lvs present

    6. Ann or bien from fibrous roots or weak taproot; stems erect or decumbent
        [Typically grows in muddy streambanks and wet seepage areas]

    6' Per from rhizomes or strong taproot

      7. Basal lvs. 0-few, not rosetted

        7a. Lower st hairs few or gen 0; lvs gen glabrous; native biennial 750-1900 m
        ..........C. pennsylvanica Willd.

        7b. Lower st hairs many; lf margins fringed with hairs; widespread European annual
        ..........C. flexuosa With.

The seeds of water cress (Rorippa nasturtium-aquaticum) are connected along both margins of the septum within each locule. In the Jepson Flora of California (1993), this species keys out under "two rows of seeds in each locule." Although Cardamine also has seeds attached in two rows, the seeds are overlapping and do not appear distinctly 2-ranked. In Rorippa the seeds appear more distinctly two-ranked, and this is apparently a defining character for the key.

See Siliques & Silicles Of The Mustard Family

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