GRISEUM Praeger, 1917
Distribution : Mexico (Guanajuato, Jalisco, Mexico, Michoacán, Querétaro, C Trans-Mexican Volcanic Belt, C Mexican Plateau).
Description (by 't Hart & Bleij in IHSP 2003) :
Perennial subshrubs with erect (or procumbent) much-branched stems with flaking bark and papillose twigs.
Leaves crowded, alternate, linear or lanceolate-linear, obtuse, sessile, (sub-)terete, finely papillose, sometimes sparingly hirtellous dorsally, often subglaucous, green, 5.9 – 28 x 1.7 – 3.2 mm, flowering branches erect or ascending.
Inflorescences cymes with 1 to many branches, pedicels to 3 mm.
Flowers 5-merous (rarely 6-merous or with 2 petals fused and thus 4-merous), sepals basally free, shortly spurred, unequal, lanceolate, ovate or lanceolate-oblong, obtuse or acute, pale green, 2.4 – 8.1 x 0.9 – 2.2 mm, erect ; petals basally connate, lanceolate, obtuse or acute, mucronate, sometimes slightly hooded, carinate, whitish, ± 7 mm, spreading to slightly recurved, anthers yellow.
Cytology : 2n = 52, 60