Calycadenia micrantha
Encyclopedia
Calycadenia micrantha is an uncommon species of flowering plant in the daisy family
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 small-flowered calycadenia. It is endemic to 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 is known from about 13 occurrences that are widely spread over several counties, including Napa
Napa County, California
Napa County is a county located north of the San Francisco Bay Area in the U.S. state of California. It is coterminous with the Napa, California, Metropolitan Statistical Area. As of 2010 the population is 136,484. The county seat is Napa....

, Trinity
Trinity County, California
Trinity County is a large, rugged and mountainous, heavily forested county located in the northwestern portion of the U.S. state of California, along the Trinity River and within the Salmon/Klamath Mountains. It covers an area of over two million acres , and as of the 2010 census its population...

, and Monterey Counties
Monterey County, California
Monterey County is a county located on the Pacific coast of the U.S. state of California, its northwestern section forming the southern half of Monterey Bay. The northern half of the bay is in Santa Cruz County. As of 2010, the population was 415,057. The county seat and largest city is Salinas...

, with several populations known in Lake County
Lake County, California
Lake County is a county located in the north central portion of the U.S. state of California, north of the San Francisco Bay Area. It takes its name from Clear Lake, the dominant geographic feature in the county and the largest natural lake wholly within California...

. It was described to science as a species in 2004. Some specimens of the plant had previously been included within the description of its relative, Calycadenia truncata
Calycadenia truncata
Calycadenia truncata is a species of flowering plant in the daisy family known by the common name Oregon western rosinweed. It is native to Oregon and northern and central California, where is a common plant in several types of habitats. This is an annual herb producing an erect stem, reddish in...

. The fact that it has been found in relatively far-flung locations suggests it could easily be present in other areas between them and, as a newly classified species, has simply not been reported yet.

This annual plant produces a slender purplish stem 10 to 50 centimeters tall. The hairy leaves are 2 to 5 centimeters long. The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...

 is a single flower head
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....

 or small cluster of heads, each with 1 to 6 three-lobed yellow ray florets. Unlike other Calycadenia
Calycadenia
Calycadenia is a genus of plants in the sunflower family known commonly as the western rosinweeds. These are found in western North America, where six of them are endemic to California, where they are mostly found in the Central Valley. Some species are quite rare...

species, this plant is self-compatible
Self-incompatibility in plants
Self-incompatibility is a general name for several genetic mechanisms in angiosperms, which prevent self-fertilization and thus encourage outcrossing...

, or able to fertilize itself.

External links

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