Slender branched perennials, 10-32 cm tall. Branches slender, erect-ascending. Leaves 15-32 x 1.5 mm, linear to linear-lanceolate, 1-nerved, sessile, glabrous, basal leaves small, scale-like, appressed to the stem. Flowers white, in racemes. Peduncle 3-12 mm long in fruit, slender. Bract 3-6(-11) mm long, linear to linear lanceolate, equalling or exceeding the flower length; bracteoles shorter than the bract, linear. Perianth infundibuliform, 2.5-3.5 mm long, 5-lobed; lobes ± 1.5 mm long, ± obtuse, cuculliform at post anthesis, one or both margins auricled. Stamens included. Filaments less than 1 mm long; anthers less than 1 mm long, oblong, yellow, adnate to the lobes by a connective of hairs. Style linear, usually included; stigma subcapitate. Nut ellipsoid to subglobose, 2.5-3 mm long, longitudinal nerves distinct, subsidiary nerves anastomosing; persistent portion of perianth 1/3 rd length of nut.

Fl. Per.: April-June.

Lectotype designated: Madden (?), N. of Choupal, Coll. ignot. (LW!).

Distribution: N. W. and W. Himalaya.

The species was described from the regions of Chepal and Pauri in Garhwal (W. Himalaya). The name Thesium himalense was first used by Royle in his ‘Ill. Bot. Him. 1:322. 1839, and validated by Edgeworth (1845); no holotype was then designated. Royle (1839) says that he collected this species. from near Choupal, N. of Choor, and allied it to Thesium liniphyllum Royle (a mss. name only). At Kew there is a gathering (i.e. N. W. India, Hb. Royle) determined as Thesium liniphyllum, which Hendrych has designated as the type of Thesium himalense, the choice of which is inappropriate as Edgeworth (1845) does not mention this gathering. These gatherings are not at K, BM or E; however at LW there is a sheet (photo!) variously determined as Thesium angulare and Thesium himalense and annotated ‘Madden, N. of Choupal’. This gathering is labelled in Royle’s handwriting Thesium angulare Royle, an unpublished name which he discarded (as evident from the label), in favour of Thesium himalense. As the label is in Royles hand and the gathering was made ‘near Choupal’ it is probable that this is the specimen referred to by Royle in his Illustrations of the Botany of the Himalayan Mountains (p. 322). The same gathering is proposed as the lectotype.

The species Thesium himalense as understood here is distinguished by having a slender habit linear leaves and tubular short flowers. Hendrych’s taxa (1962), namely Thesium thomsonii and Thesium indicum, the types of which I have examined at Kew, are identical with Thesium himalense; they have the same narrow leaves and similar flowers.

Thesium himalense is an uncommon species and appears to be under-collected in the Himalaya. It is found from altitudes between 900-2134 m and does not appear to exceed this upper limit.