Madia exigua
Encyclopedia
Madia exigua is a species of flowering plant in the aster family
known by the common names small tarweed and threadstem madia.
to Baja California
, where it grows in many types of dry habitat outside the deserts.
The inflorescence
is an array of clustered flower heads
on thin, stiff peduncles
. Each head has an involucre of phyllaries
shaped like a top
. The phyllaries are coated in knobby yellow resin glands. At the tip of the inflorescence are minute yellowish ray florets each under a millimeter long, and one or two yellow disc florets. The fruit is an achene
with no pappus
.
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 names small tarweed and threadstem madia.
Range
Madia exigua is native to western North America from British ColumbiaBritish Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
to Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, where it grows in many types of dry habitat outside the deserts.
Description
Madia exigua is an aromatic annual herb growing up to half a meter (20") tall, its slender stem coated with hairs, large stalked resin glands, and sometimes bristles. The rough-haired leaves are 1 to 4 centimeters (0.4 to 1.6") 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 an array of clustered flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
on thin, stiff peduncles
Peduncle (botany)
In botany, a peduncle is a stem supporting an inflorescence, or after fecundation, an infructescence.The peduncle is a stem, usually green and without leaves, though sometimes colored or supporting small leaves...
. Each head has an involucre of 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...
shaped like a top
Top
A top is a toy that can be spun on an axis, balancing on a point. This motion is produced in the most simple forms of top by twirling the stem using the fingers. More sophisticated tops are spun by by holding the axis firmly while pulling a string or twisting a stick or pushing an auger as shown...
. The phyllaries are coated in knobby yellow resin glands. At the tip of the inflorescence are minute yellowish ray florets each under a millimeter long, and one or two yellow disc florets. 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 no 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...
.