Question: Which Genus has around 30 species of flowering plants, Schoenoplectus or Isatis?
Context: Trachysphaera is a genus of pill millipedes in the order Glomerida.  Around 30 species are known, making it the third most species-rich genus of Glomerida.  "Trachysphaera" species are patchily distributed throughout Europe and western Asia, extending from Spain to Caucasia. Sagina (like "Colobanthus" called "pearlworts") is a genus of 20–30 species of flowering plants in the pink or carnation family, Caryophyllaceae.  These are flowering herbs native to temperate regions of the Northern Hemisphere extending south to tropical mountain areas at high altitudes, reaching just south of the equator in Africa.  They are small annual or perennial herbaceous plants, growing to 5–15 cm.  The leaves are opposite, often in tight whorl-like clusters, simple linear, typically 5–20 mm long.  The flowers are solitary or in small cymes, with four or five green sepals and an equal number of white petals; the petal size relative to the sepal size is useful in species identification.  The fruit is a small capsule containing several seeds. Baumea is a genus of the sedge family, which includes around 30 species native to Madagascar and the Pacific Islands, with 15 species in Australia.  All are perennial rhizomatous herbs, with leaves and stems very similar in appearance.  The inflorescence is terminal, with the flowers tightly clustered or loosely arranged.  The fruits are small nuts. Mazus is a genus of low-growing perennial plants.  It has been placed in various plant families including Phrymaceae, Scrophulariaceae, and recently in the family Mazaceae.  Consisting of around 30 species, this genus is generally found in damp habitats in lowland or mountain regions of China, Japan, Southeast Asia, Australia and New Zealand. Sambucus is a genus of flowering plants in the family Adoxaceae.  The various species are commonly called elder or elderberry.  The genus was formerly placed in the honeysuckle family, Caprifoliaceae, but was reclassified as Adoxaceae due to genetic and morphological comparisons to plants in the genus "Adoxa".  In "Sambucus", there are between 5 and 30 species of deciduous shrubs, small trees and herbaceous perennial plants. Priocnemus is a genus of pepsine spider wasp containing around 30 species Schoenoplectus (club-rush [Old World species], bulrush or tule [New World species]) is a genus of plants in the sedges with a cosmopolitan distribution.  Note that the name bulrush is also applied to species in the unrelated genus "Typha" as well as to other sedges.  The genus "Schoenoplectus" was formerly considered part of "Scirpus", but recent phylogenetic data shows that they are not closely related. Isatis is a genus of about 30 species of flowering plants in the family Brassicaceae, native to the Mediterranean region east to central Asia.  The genus includes woad ("Isatis tinctoria"). Porterella is a monotypic genus of flowering plants in the bellflower family containing the single species Porterella carnosula, which is known by the common name fleshy porterella, or simply porterella.  It is native to the western United States from California to Wyoming, where it grows in moist spots, such as ponds or wet grasslands, sometimes just at the edge of the water or partially submerged.  It is an annual herb producing an erect stem to a maximum height around 30 centimeters.  The leaves along the stem are oval or triangular, those growing beneath the surface of the water more triangular in shape.  They measure up to 1.5 centimeters long by half a centimeter wide.  The inflorescence bears showy flowers which are quite similar in appearance to those of some species in sister genus "Downingia".  Each has a narrow tubular throat opening into a wide corolla with two narrow pointed upper lobes and three wider, rounded lower lobes each with a small tooth.  The upper lobes are deep blue, and the lower lobes are a similar shade with an area of white and bright yellow near the throat.  The stamens are fused into a single unit tipped with tiny toothlike anthers. Navarretia is a genus of about 30 species of flowering plants related to the phloxes and the gilias.  This is one genus of plants, among others, which are sometimes called pincushionplants.  The inflorescence which bears the flowers is surrounded by frilly green bracts bearing soft spines, giving it the appearance of a pincushion.  Several species are members of the vernal pool ecosystem.
Answer: Isatis