''Dudleya caespitosa'' is a

succulent plant In botany, succulent plants, also known as succulents, are plants with parts that are thickened, fleshy, and engorged, usually to retain water in arid climates or soil conditions. The word ''succulent'' comes from the Latin word ''sucus'', meanin ...

known by several common names, including sea lettuce, sand lettuce, and coast dudleya. It is

endemic Endemism is the state of a species being found only 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 foun ...

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, where it grows along the coastline in the southern half of the state. Taxonomically, this species is a highly variable

complex Complex commonly refers to: * Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe ** Complex system, a system composed of many components which may interact with each ...

of polymorphic and

polyploid Polyploidy is a condition in which the biological cell, cells of an organism have more than two paired sets of (Homologous chromosome, homologous) chromosomes. Most species whose cells have Cell nucleus, nuclei (eukaryotes) are diploid, meaning ...

plants, closely related to numerous neighboring species such as '' Dudleya farinosa'', '' Dudleya greenei'' and '' Dudleya palmeri''. It is delimited from neighboring species on an arbitrary basis of distribution and chromosome number, and may not be immediately separable from the other species it approaches.

Description

Vegetative morphology

This plant may grow in solitary rosettes, but most often forms caespitose clumps, which may contain up to 150+ rosettes. The clumps are generally not dense. Each rosette may be anywhere from 8 to 32 cm wide, containing 15 to 30 leaves. The

caudex A caudex (: caudices) of a plant is a stem, but the term is also used to mean a rootstock and particularly a basal stem structure from which new growth arises.pages 456 and 695 In the strict sense of the term, meaning a stem, "caudex" is most ...

is 1.5 to 4 cm wide, and on older plants is often exposed between dry

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

. The stem is not swollen at the base, unlike '' D. candelabrum''. It has a longer stem compared to '' D. farinosa'' due to greater space between the

internodes A stem is one of two main structural axes of a vascular plant, the other being the root. It supports leaves, flowers and fruits, transports water and dissolved substances between the roots and the shoots in the xylem and phloem, engages in pho ...

. The

leaf shape The following terms are used to describe leaf morphology in the description and taxonomy of plants. Leaves may be simple (that is, the leaf blade or 'lamina' is undivided) or compound (that is, the leaf blade is divided into two or more leaflets ...

is extremely variable, although often lance-oblong, or oblong to oblanceolate, with generally acute to sub-acuminate leaf tips. On the edge of the leaf (the margin), there is generally ''not'' an angle between the upper and lower leaf surfaces. The leaf dimensions are generally around 5 to 20 cm long, 1 to 2 cm wide, and 3 to 8 cm thick, with the base of the leaf 0.5 to 4 cm wide.

Reproductive morphology

The peduncle is generally 10 to 60 cm tall, and 3.5 to 10 mm wide. There are typically 3 to 5 first degree branches on the

inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branches. An inflorescence is categorized on the basis of the arrangement of flowers on a mai ...

, which may stay simple or rebranch up to two times. The branches do not twist, and the flowers are on the topside. Each terminal branch is 3 to 15 cm long, and contains 4 to 15

flower Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

s. There are 12 to 25 bracts, spreading to ascending, and shaped triangular ovate to lanceolate. The

pedicels In botany, a pedicel is a stem that attaches a single flower to the inflorescence In botany, an inflorescence is a group or cluster of flowers arranged on a plant's Plant stem, stem that is composed of a main branch or a system of branch ...

are 1 to 6 mm long, erect, and not bent in fruit. The

sepal A sepal () is a part of the flower of angiosperms (flowering plants). Usually green, sepals typically function as protection for the flower in bud, and often as support for the petals when in bloom., p. 106 Etymology The term ''sepalum'' ...

s are 2 to 5 mm long, and shaped deltate-ovate, with an acute tip. The

petal Petals are modified leaves that form an inner whorl surrounding the reproductive parts of flowers. They are often brightly coloured or unusually shaped to attract pollinators. All of the petals of a flower are collectively known as the ''corol ...

s are 8 to 16 mm long, 3 to 5 mm wide, shaped elliptic, and are connate (fused to form a tubular corolla, as seen in the subgenus '' Dudleya'') 1.5 to 2.5 mm. The

s have an acute apex with erect tips, and are generally colored bright yellow to orange yellow or red.

Taxonomy

Taxonomic history

The plant was first described in 1803 by

Adrian Hardy Haworth Adrian Hardy Haworth (19 April 1767, in Kingston upon Hull, Hull – 24 August 1833, in Chelsea, London, Chelsea) was an England, English entomologist, botanist and carcinologist. Family The younger son of Benjamin Haworth, of Haworth Hall and ...

as ''Cotyledon caespitosa'' (the

basionym In the scientific name of organisms, basionym or basyonym means the original name on which a new name is based; the author citation of the new name should include the authors of the basionym in parentheses. The term "basionym" is used in both botan ...

). The original text erroneously cited it as from the

Cape of Good Hope The Cape of Good Hope ( ) is a rocky headland on the Atlantic Ocean, Atlantic coast of the Cape Peninsula in South Africa. A List of common misconceptions#Geography, common misconception is that the Cape of Good Hope is the southern tip of Afri ...

. The same species would later be described again as ''Sedum cotyledon'' by

Joseph Franz von Jacquin Joseph "Krystel" Franz Freiherr von Jacquin or Baron Joseph von Jacquin (7 February 1766, in Schemnitz (now Banská Štiavnica) – 26 October 1839, in Vienna) was an Austrian scientist who studied medicine, chemistry, zoology and botany. ...

and as ''Cotyledon linguiformis'' by

Brown Brown is a color. It can be considered a composite color, but it is mainly a darker shade of orange. In the CMYK color model used in printing and painting, brown is usually made by combining the colors Orange (colour), orange and black. In the ...

, both in 1811. In 1849, Lindley described the plant as ''Echeveria laxa'', noting it as a very distinct looking plant, "but not one that is handsome." The plant was described in its current form by Nathaniel Lord Britton and Joseph Nelson Rose in their revision of North American Crassulaceae, which created the genus ''Dudleya''.

Species complex

''Dudleya caespitosa'' is regarded as a member of a highly developed polyploid complex involving numerous neighboring taxa, including '' Dudleya farinosa'', '' Dudleya greenei'', '' Dudleya palmeri'', '' Dudleya lanceolata'', '' Dudleya cymosa'' and '' Dudleya candelabrum''. Reid Moran and Charles H. Uhl arbitrarily separated this species on the basis of ploidy and distribution. ''Dudleya greenei'' is an insular segregate of ''Dudleya caespitosa'', whilst ''Dudleya palmeri'' is on the fringe of the complex with wide leaves and red to orange petals.

Distribution and habitat

This plant is common and is found along the coast of California. Because the delimitation of the plant is based on arbitrary characteristics, the exact biogeographical distribution is difficult to pin down. The 2012 Jepson Treatment places the northern limit on the southern North Coast of the California Floristic Province. Plants identified with ''Dudleya caespitosa'' are found in the north from

Point Reyes Point Reyes ( , meaning 'Cape of the Kings') is a prominent landform and popular tourist destination on the Pacific coast of Marin County in Northern California. It is approximately west-northwest of San Francisco. The term is often applied ...

south to Malibu.

Ecology

On the central coast of California near Santa Maria, numerous

oil refineries An oil refinery or petroleum refinery is an industrial process plant where petroleum (crude oil) is transformed and refined into products such as gasoline (petrol), diesel fuel, asphalt base, fuel oils, heating oil, kerosene, liquefied pet ...

exist, pumping phytotoxic

sulfur dioxide Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a colorless gas with a pungent smell that is responsible for the odor of burnt matches. It is r ...

. While plants like ''

Salvia mellifera ''Salvia mellifera'' (Californian black sage, also known as seel by the Mahuna) is a small, highly aromatic, evergreen shrub of the genus ''Salvia'' (the sages) native to California, and Baja California, Mexico. It is common in the coastal sage ...

'' (black sage) were affected, ''Dudleya caespitosa'' proved to be somewhat tolerant of the emissions. This is likely due to the fact that ''Dudleya caespitosa'' uses CAM photosynthesis, which means their stomata open in the evening hours. Combined with the effect of southeast winds at night that blow away the emissions, the ''Dudleya'' avoid the phytotoxic emissions through this combination of

meteorological Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agriculture ...

conditions and CAM photosynthesis.

References

External links

Jepson Manual Treatment: ''Dudleya caespitosa''

USDA Plants Profile: ''Dudleya caespitosa''

''Dudleya caespitosa'' — U.C. Photo gallery
{{Taxonbar, from=Q8770906 caespitosa Endemic flora of California Natural history of the California chaparral and woodlands Natural history of the Santa Monica Mountains Garden plants of North America Drought-tolerant plants Taxa named by Joseph Nelson Rose Taxa named by Nathaniel Lord Britton