''Lessingia micradenia'' is a rare species of flowering plant in the family
Asteraceae
The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae ...
known by the common name Mt. Tamalpais lessingia. It is
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...
to the
San Francisco Bay Area
The San Francisco Bay Area, often referred to as simply the Bay Area, is a populous region surrounding the San Francisco, San Pablo, and Suisun Bay estuaries in Northern California. The Bay Area is defined by the Association of Bay Area Gov ...
of
California
California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...
, where it occurs in areas with
serpentine soils. 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, officially the County of Santa Clara, is the sixth-most populous county in the U.S. state of California, with a population of 1,936,259, as of the 2020 census. Santa Clara County and neighboring San Benito County together f ...
south of
San Jose, while var. ''micradenia'' is known only from a few spots around
Mount Tamalpais
Mount Tamalpais (; ; Miwok: ''Támal Pájiṣ''), known locally as Mount Tam, 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 Moun ...
in
Marin County
Marin County is a county located in the northwestern part of the San Francisco Bay Area of the U.S. state of California. As of the 2020 census, the population was 262,231. Its county seat and largest city is San Rafael. Marin County is a ...
.
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
A pseudanthium (Greek for "false flower"; ) is an inflorescence that resembles a flower. The word is sometimes used for other structures that are neither a true flower nor a true inflorescence. Examples of pseudanthia include flower heads, compos ...
appear singly or in clusters. Each head is lined with purple-tipped, glandular
phyllaries
In botanical terminology, a phyllary, also known an involucral bract or tegule, is a single bract of the involucre of a composite flower. The involucre is the grouping of bracts together. Phyllaries are reduced leaf-like structures that form one ...
. 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
An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not op ...
with
pappus of five distinct whitish points.
References
External links
Jepson Manual TreatmentUSDA Plants ProfileFlora of North AmericaPhoto gallery: var. ''glabrata''Photo gallery: var ''micradenia''
micradenia
Endemic flora of California
Endemic flora of the San Francisco Bay Area
{{Astereae-stub