Lessingia micradenia
Encyclopedia
Lessingia micradenia is a rare species of flowering plant in the daisy family
known by the common name Mt. Tamalpais lessingia. It is endemic to the San Francisco Bay Area
of California
, where it occurs in areas with serpentine soil
s. The species is divided into two rare varieties, each with a limited occurrence on opposite sides of the Bay Area. Lessingia micradenia var. glabrata is found in several locations across Santa Clara County
south of San Jose
, while var. micradenia is known only from a few spots around Mount Tamalpais
in Marin County
.
This is a slender annual herb growing erect and varying in size from just a few centimeters to over half a meter tall, with spreading branches. It is often hairy or woolly in texture. The upper leaves are small and pointed, no more than 2 centimeters long, and the lower leaves are longer and wither early. The petite flower heads
appear singly or in clusters. Each head is lined with purple-tipped, glandular phyllaries
. The head is discoid, containing no ray florets but a few funnel-shaped, lobed disc florets in shades of light purple to nearly white. The fruit is an achene
with pappus
of five distinct whitish points.
Asteraceae
The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...
known by the common name Mt. Tamalpais lessingia. It is endemic to the San Francisco Bay Area
San Francisco Bay Area
The San Francisco Bay Area, commonly known as the Bay Area, is a populated region that surrounds the San Francisco and San Pablo estuaries in Northern California. The region encompasses metropolitan areas of San Francisco, Oakland, and San Jose, along with smaller urban and rural areas...
of California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, where it occurs in areas with serpentine soil
Serpentine soil
A serpentine soil is derived from ultramafic rocks, in particular serpentinite, a rock formed by the hydration and metamorphic transformation of ultramafic rock from the Earth's mantle....
s. The species is divided into two rare varieties, each with a limited occurrence on opposite sides of the Bay Area. Lessingia micradenia var. glabrata is found in several locations across Santa Clara County
Santa Clara County, California
Santa Clara County is a county located at the southern end of the San Francisco Bay Area in the U.S. state of California. As of 2010 it had a population of 1,781,642. The county seat is San Jose. The highly urbanized Santa Clara Valley within Santa Clara County is also known as Silicon Valley...
south of San Jose
San Jose, California
San Jose is the third-largest city in California, the tenth-largest in the U.S., and the county seat of Santa Clara County which is located at the southern end of San Francisco Bay...
, while var. micradenia is known only from a few spots around Mount Tamalpais
Mount Tamalpais
Mount Tamalpais is a peak in Marin County, California, United States, often considered symbolic of Marin County. Much of Mount Tamalpais is protected within public lands such as Mount Tamalpais State Park and the Mount Tamalpais Watershed.-Geography:...
in Marin County
Marin County, California
Marin County is a county located in the North San Francisco Bay Area of the U.S. state of California, across the Golden Gate Bridge from San Francisco. As of 2010, the population was 252,409. The county seat is San Rafael and the largest employer is the county government. Marin County is well...
.
This is a slender annual herb growing erect and varying in size from just a few centimeters to over half a meter tall, with spreading branches. It is often hairy or woolly in texture. The upper leaves are small and pointed, no more than 2 centimeters long, and the lower leaves are longer and wither early. The petite flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
appear singly or in clusters. Each head is lined with purple-tipped, glandular phyllaries
Bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
. The head is discoid, containing no ray florets but a few funnel-shaped, lobed disc florets in shades of light purple to nearly white. The fruit is an achene
Achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...
with pappus
Pappus (flower structure)
The pappus is the modified calyx, the part of an individual disk, ray or ligule floret surrounding the base of the corolla, in flower heads of the plant family Asteraceae. The pappus may be composed of bristles , awns, scales, or may be absent. In some species, the pappus is too small to see...
of five distinct whitish points.