Question: Between Exacum and Mahonia, which plant genus has about 70 species?
Context: Mahonia is a genus of about 70 species of evergreen shrubs in the family Berberidaceae, native to eastern Asia, the Himalaya, North America, and Central America.  They are closely related to the genus "Berberis".  Botanists disagree on the acceptability of the genus name "Mahonia".  Several authorities argue plants in this genus should be included in the genus "Berberis" because several species in both genera are able to hybridize, and because when the two genera are looked at as a whole, there is no consistent morphological separation except simple vs compound leaves.  "Mahonia" typically have large, pinnate leaves 10–50 cm long with five to fifteen leaflets, and flowers in racemes which are 5–20 cm long. Porphyra is a coldwater seaweed that grows in cold, shallow seawater.  More specifically, it belongs to red algae phylum of laver species, comprising approximately 70 species.  It grows in the intertidal zone, typically between the upper intertidal zone and the splash zone in cold waters of temperate oceans.  In East Asia, it is used to produce the sea vegetable products "nori" (in Japan) and "gim" (in Korea).  There are considered to be 60 to 70 species of "Porphyra" worldwide and seven in the British Isles. Berberis and Mahonia are two widespread and common members of the Berberidaceae, found in many countries.  Botanists have for many years had no consensus on the classification, some preferring to treat the group as a single genus ("Berberis"), while others opt to separate the two groups into distinct genera.  Therefore, many species have two scientific name, one in "Berberis", the other in "Mahonia", each used by botanists on one side the debate. Berberis standleyi is a shrub in the Berberidaceae described as a species in 1952.  It was published with the name "Mahonia glauca," a very different plant from "Berberis glauca."  Thus if one desires to consider "Berberis" and "Mahonia" as one genus instead of two, it is necessary to use a different name, i.e. "Berberis standleyi". Agalinis acuta is an annual hemiparasitic plant native to Maryland, Massachusetts, Rhode Island, Connecticut, and Long Island, New York.  Common names include sandplain gerardia and sandplain false foxglove.  It is one of about 70 species that comprise genus "Agalinis".  It currently resides within the family Orobanchaceae, but historically was aligned with members of the Scrophulariaceae.  This was one of several re-alignments that were the consequence of the disintegration of the Scrophulariaceae as the result of conclusions based on molecular phylogeny data from the chloroplast genome.  While historically regarded as a separate species, molecular phylogenetic data indicates that "Agalinis acuta" should be consolidated as part of the species "Agalinis decemloba". Dipterocarpaceae are a family of 16 genera and approximately 695 known species of mainly tropical lowland rainforest trees.  The family name, from the type genus "Dipterocarpus", is derived from Greek ("di" = two, "pteron" = wing and "karpos" = fruit) and refers to the two-winged fruit.  The largest genera are "Shorea" (196 species), "Hopea" (104 species), "Dipterocarpus" (70 species), and "Vatica" (65 species).  Many are large forest emergent species, typically reaching heights of 40–70 m, some even over 80 m (in the genera "Dryobalanops", "Hopea" and "Shorea"), with the tallest known living specimen ("Shorea faguetiana") 93.0 m tall.  The species of this family are of major importance in the timber trade.  Their distribution is pantropical, from northern South America to Africa, the Seychelles, India, Indochina, Indonesia and Malaysia.  The greatest diversity of Dipterocarpaceae occurs in Borneo.  Some species are now endangered as a result of overcutting, extensive illegal logging and habitat conversion.  They provide valuable woods, aromatic essential oils, balsam, resins and are a source for plywood. Banksia sessilis, commonly known as parrot bush, is a species of shrub or tree in the plant genus "Banksia" in the family Proteaceae.  It had been known as Dryandra sessilis until 2007, when the genus "Dryandra" was sunk into "Banksia".  The Noongar peoples know the plant as Budjan or Butyak.  Widespread throughout southwest Western Australia, it is found on sandy soils over laterite or limestone, often as an understorey plant in open forest, woodland or shrubland.  Encountered as a shrub or small tree up to 6 m in height, it has prickly dark green leaves and dome-shaped cream-yellow flowerheads.  Flowering from winter through to late spring, it provides a key source of food—both the nectar and the insects it attracts—for honeyeaters in the cooler months, and species diversity is reduced in areas where there is little or no parrot bush occurring.  Several species of honeyeater, some species of native bee, and the European honey bee seek out and consume the nectar, while the long-billed black cockatoo and Australian ringneck eat the seed.  The life cycle of "Banksia sessilis" is adapted to regular bushfires.  Killed by fire and regenerating by seed afterwards, each shrub generally produces many flowerheads and a massive amount of seed.  It can recolonise disturbed areas, and may grow in thickets. Mammea is a flowering plant genus with about 70 species in the family Calophyllaceae.  Its members are evergreen trees having edible fruits.  The flowers are polygamous, with a unitary calyx opening into two or three valvate sepals.  There are 4 to 8 petals. Berries are formed, containing 1 to 4 seeds.  The leaves are rigid, coriaceous and often have pellucid dots. Exacum is a genus of plant in family Gentianaceae.  It contains the following species (but this list is incomplete): Exacum affine (syn.  "Exacum socotranum", "Exacum gracilipes") known commercially as the Persian violet, is a species of plant in the family Gentianaceae.  It is endemic to Socotra, part of Yemen, though its popularity and cultivation around the world have made it an occasional greenhouse weed.  Its natural habitat is rocky areas.  A small herbaceous biennial plant with dark green, ovate leaves.  The small purple flowers have a yellow centre with fragrance.
Answer: Mahonia