Plantago arenaria

Two subspecies are recognized: P. arenaria arenaria, the nominate subspecies; and P. arenaria orientalis (Soó) Greuter & Burdet. Each of these subspecies is known under a large number of taxonomic synonyms.[5][6]

Plantago arenaria is an annual herb with a taproot that has an erect stem with leaves that are usually opposite but sometimes in whorls of 3, and elongated internodes between leaf sets.[2][7] Glandular pubescence is found on the stems, leaves, sepals, and inflorescences.[2] The leaves are simple and have a base that is decurrent onto the petiole, an entire or slightly dentate edge, are linear or lanceolate in shape, and can reach 2.5-5cm long and 1-3mm wide.[2][7] Some leaves are modified into bracts between 0.5cm and 2cm which have a cuspidate apex and an orbicular-ovate base.[2] The plant has a densely flowered inflorescence with flowers that have a glabrous, brownish corolla and a calyx with broadly veined, elliptic and obovate sepals.[2][7] The stamens exsert above the corolla, and the anthers are yellow, ellipsoid, and 1.8-2.2mm in size.[2][7] The style of the stigma is also well exserted, and the floral parts are hypogynous but extend superior to the ovary.[2][3][7] The seeds are contained in capsules of 2. The seeds are 2.5-2.8 mm in size, black or blackish-brown, shiny, ellipsoid, and have a distinct central groove on the inner face.[2][7]

Plantago arenaria is described as being native to North Africa, Southwest China, Europe, Russia, Kazakhstan, Kyrgyzstan, Russia, and Tajikistan.[2] The plant has become broadly naturalized, identified in areas of Australia, North America, India, Japan, and Pakistan.[2][3] The plant is commonly found in sandy areas such as in arid deserts and on sandy beaches, and has also been seen distributed on roadsides, and by railroad tracks.[2][3][8][9]

Illustration showing overall plant morphology, including flowers and seeds.

The seeds, known as French psyllium or black psyllium, are medicinally cultivated, along with other species under the psyllium common name, such as P. ovata, for use as a laxative for constipation and are also used to treat irritable bowel syndrome (IBS) and diarrhea by extracting the mucilage from the seed coat.[4][10] The mucilage from the seeds has also been reported to lower the risk of coronary heart disease.[4][10]