Question: Which genus of plant is part of the daisy family, Zinnia or Pachypodium?
Context: Erigeron serpentinus is a rare species of flowering plant in the daisy family known by the common names serpentine fleabane and serpentine daisy.  It is endemic to Sonoma County, California, where it is known from three occurrences in and around The Cedars, in the Coast Ranges east of Salt Point and west of Healdsburg.  There are an estimated 1100 individuals in existence.  The Cedars is a canyon habitat with serpentine soils surrounded by non-serpentine terrain; it is home to several rare serpentine-endemic plant species.  This daisy was discovered there and described to science in 1992. Erigeron annuus (annual fleabane, daisy fleabane, or eastern daisy fleabane) is a North American plant species in the daisy family. Pachypodium is a genus of succulent spine-bearing trees and shrubs, native to Madagascar and Africa.  It belongs to the dogbane family, Apocynaceae.  "Pachypodium" comes from a Latin form from Greek "pachus" (thick) and "podion" (foot) (or Gk podos, root form of pous, foot), hence meaning "thick-footed". Gundelia is a low to high (20–100 cm) thistle-like perennial herbaceous plant with latex, spiny compound inflorescences, reminiscent of teasles and eryngos, that contain cream, yellow, greenish, pink, purple or redish-purple disk florets.  It is assigned to the daisy family.  Flowers can be found from February to May.  The stems of this plant dry-out when the seeds are ripe and break free from the underground root, and are then blown away like a tumbleweed, thus spreading the seeds effectively over large areas with little standing vegetation.  This plant is native to the eastern Mediterranean and the Middle-East.  Opinions differ about the number of species in "Gundelia".  Sometimes the genus is regarded monotypic, Gundelia tournefortii being a species with a large variability, but other authors distinguish up to nine species, differing in floret color and pubescence.  Young stems are cooked and eaten in the Middle-East and are said to taste like a combination of artichoke and asparagus.  The plant also contains compounds that have been demonstrated to be effective against a range of ailments.  A large quantity of pollen assigned to "Gundelia" has been found on the Shroud of Turin, which may suggest that the crown of thorns was made from "Gundelia", but this finding has been contested. Pleurophyllum hookeri, also known as the Silver-leaf Daisy or Sage-green Rosette Herb, is a herbaceous plant in the daisy family, a megaherb native to the subantarctic Auckland and Campbell Islands of New Zealand and Australia’s Macquarie Island.  It grows up to 900 mm in height and has crimson button flowers and long, silky, silver leaves, with a large carrot-like tuber and long roots.  It also has the unusual feature of a vertically contractile stem, most of which is underground, which serves to keep the leaf rosette close to the ground surface and the plant anchored securely against the very strong winds typical of subantarctic islands.  It is threatened on Macquarie Island by introduced black rats and European rabbits. Erigeron compactus is a species of flowering plant in the daisy family known by the common names cushion daisy, fernleaf fleabane, and compact daisy. Hesperevax caulescens is a small flowering plant in the daisy family.  One common name for the plant is hogwallow starfish, as it is a somewhat flat, star-shaped plant which grows in mud.  Another common name is dwarf dwarf-cudweed, as the three members of genus "Hesperevax" are known as dwarf-cudweeds and this species is smaller than the others.  It may also be called involucrate evax, since its former Latin name was "Evax involucrata".  This annual plant is a member of the vernal pool plant community in California, where it is possibly an endemic species, although its range might extend into Baja California.  The hogwallow starfish radiates pale green spoon-shaped leaves in a basal rosette and extends a short erect stem.  The flowers are less than two millimeters wide.  This species grows along the outskirts of vernal pools in areas which have dried. Grindelia stricta is a species of flowering plant in the daisy family known by the common names Oregon gumplant, Oregon gumweed and (in Britain and Ireland) coastal gumplant.  It is native to the west coast of North America from California to Alaska, where it is a resident of coastal plant communities such as those in marshes and beaches.  This plant is variable in appearance, taking the form of a weedlike perennial herb forming low clumps to a sprawling subshrub growing erect to heights exceeding one meter.  Its foliage and stems are green to rusty red or purplish and the plant may be hairy to hairless.  The fleshy leaves are green, often with red edges and veining, and are up to 15 centimeters in length on large plants.  The inflorescence holds one or more flower heads each up to 5 centimeters wide.  The flower head is a cup of thick erect or recurved green phyllaries.  Yellow disc florets fill the center of the flower head and there is a fringe of yellow ray florets around the circumference.  The head produces copious white exudate, especially in the early stages of blooming. Zinnia is a genus of plants of the sunflower tribe within the daisy family.  They are native to scrub and dry grassland in an area stretching from the Southwestern United States to South America, with a centre of diversity in Mexico.  Members of the genus are notable for their solitary long-stemmed flowers that come in a variety of bright colors.  The genus name honors German master botanist Johann Gottfried Zinn (1727–59). Tridax procumbens, commonly known as coatbuttons or tridax daisy, is a species of flowering plant in the daisy family.  It is best known as a widespread weed and pest plant.  It is native to the tropical Americas, but it has been introduced to tropical, subtropical, and mild temperate regions worldwide.  It is listed as a noxious weed in the United States and has pest status in nine states.
Answer: Zinnia