''Streptanthus callistus'' is a rare species of flowering plant in the

mustard family Brassicaceae () or (the older but equally valid) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some ar ...

known by the common name Mount Hamilton jewelflower. 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 ...

Santa Clara County, California 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 United States census, 2020 census. Santa Clara County and neighboring Sa ...

, where it is known from only about five occurrences around Mount Hamilton.The Nature Conservancy
/ref> It grows in

chaparral Chaparral ( ) is a shrubland plant plant community, community found primarily in California, southern Oregon, and northern Baja California. It is shaped by a Mediterranean climate (mild wet winters and hot dry summers) and infrequent, high-intens ...

and woodlands and on dry

scree Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. The term ''scree'' is ap ...

. It is an annual herb producing a small stem up to 8 or 9 centimeters tall with a bristly base. The toothed oval leaves are under 2 centimeters long. 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 ...

is a cluster-like

raceme A raceme () or racemoid is an unbranched, indeterminate growth, indeterminate type of inflorescence bearing flowers having short floral stalks along the shoots that bear the flowers. The oldest flowers grow close to the base and new flowers are ...

of flowers, the top ones sterile. The fertile flowers on the lower raceme have calyces of bristly purple-green

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 under a centimeter long with flaring purple petals at the tip. The sterile flowers at the top of the raceme have narrow, elongated, hairless purple sepals. The fruit is a cylindrical, bristle-studded

silique A silique or siliqua (plural ''siliques'' or ''siliquae'') is a type of fruit (seed capsule) having two fused carpels with the length being more than three times the width. When the length is less than three times the width of the dried fruit ...

measuring up to 2 or 2.5 centimeters long.

References

External links

Jepson Manual TreatmentPhoto gallery
callistus Natural history of Santa Clara County, California Endemic flora of California Endemic flora of the San Francisco Bay Area {{Brassicales-stub