Question: Which plant’s genus has the most other species, Purshia or Bergerocactus?
Context: Bergerocactus emoryi (golden cereus, golden-spined cereus, golden snakecactus) is a species of cactus.  It is the sole member of the genus Bergerocactus, named after Alwin Berger.  The plant is also known as snake cactus, though this latter name also applies to "Echinocereus pensilis". Cladosporium is a genus of fungi including some of the most common indoor and outdoor molds. Species produce olive-green to brown or black colonies, and have dark-pigmented conidia that are formed in simple or branching chains.  Many species of "Cladosporium" are commonly found on living and dead plant material.  Some species are plant pathogens, others parasitize other fungi.  "Cladosporium" spores are wind-dispersed and they are often extremely abundant in outdoor air.  Indoors "Cladosporium" species may grow on surfaces when moisture is present. " Cladosporium fulvum", cause of tomato leaf mould, has been an important genetic model, in that the genetics of host resistance are understood.  In the 1960s, it was estimated that the genus "Cladosporium" contained around 500 plant-pathogenic and saprotrophic species, but this number has since been increased to over 772 species.  The genus "Cladosporium" is closely related to black yeasts in the order Dothideales.  "Cladosporium" species are often highly osmotolerant, growing easily on media containing 10% glucose or 12–17% NaCl.  They are rarely grown on media containing 24% NaCl or 50% glucose and never isolated from medium with 32% NaCl or greater.  Most species have very fragile spore chains, making it extremely difficult to prepare a mount for microscopic observation in which the conidial chains are preserved intact. Purshia stansburyana is a species of flowering plant in the rose family known by the common name Stansbury's cliffrose.  It is native to the southwestern United States and northern Mexico, where it grows in woodlands, desert, and plateau habitat.  It often grows anchored on cliffs and prefers rocky, granular soils, especially limestone. Lophodermium is a genus of fungi within the family Rhytismataceae.  The genus contains 145 species and has a global distribution.  Species of this genus are usually observed producing zone lines, conidiomata and ascomata on dead fallen leaves, but at least some are known to colonize living leaves.  In many cases they then live inside the colonized leaf as a symptomless endobiont, where they are regarded as detritivores utilising dead plant matter.  In a few cases they may kill all or part of the leaf prematurely, and there is a substantial literature dealing with those species as plant pathogens.  The genus infects many different plant families but with a notable concentration in the family Pinaceae; many "Lophodermium" species are restricted to a single host genus (or even species), but some, particularly those infecting grasses, may infect several genera.  Some are economically important plant pathogens, such as those that cause needlecast disease in European Black Pine, Scots Pine and Red Pine in forestry and christmas tree plantations.  In these species, notably "L. pinastri" and "L. seditiosum", the fungal spores disperse and infect the pine needles in late summer, which turn brown by the following spring and then fall off. × "Pacherocactus is a genus of shrubby cactus, with only one known species, × "Pacherocactus orcuttii.  It is a natural hybrid between "Pachycereus pringlei" and "Bergerocactus emoryi", discovered near Rosario, Baja California, Mexico.  The plant's generic name is formed from those of its parents ("Pachycereus" and "Bergerocactus"); sometimes it can be found listed as "Pachycereus" × "Bergerocactus". × "Myrtgerocactus lindsayi is a species of cacti, the only one in the hybrid genus × "Myrtgerocactus.  It is thought to be a natural hybrid between "Myrtillocactus cochal" and "Bergerocactus emoryi".  Its generic name comes from those of its parents ("Mytillocactus" and "Bergerocactus") and its specific epithet, ""lindsayi"", is in honor of the botanist George Lindsay. Purshia (bitterbrush or cliff-rose) is a small genus of 5-8 species of flowering plants in the family Rosaceae, native to western North America, where they grow in dry climates from southeast British Columbia in Canada south throughout the western United States to northern Mexico.  The classification of "Purshia" within the Rosaceae has been unclear.  The genus was originally placed in the subfamily Rosoideae, but is now placed in subfamily Dryadoideae. A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place".  Examples commonly are plants unwanted in human-controlled settings, such as farm fields, gardens, lawns, and parks. Taxonomically, the term "weed" has no botanical significance, because a plant that is a weed in one context is "not" a weed when growing in a situation where it "is" in fact wanted, and where one species of plant is a valuable crop plant, another species in the same genus might be a serious weed, such as a wild bramble growing among cultivated loganberries.  Many plants that people widely regard as weeds also are intentionally grown in gardens and other cultivated settings, in which case they are sometimes called beneficial weeds.  The term "weed" also is applied to any plant that grows or reproduces aggressively, or is invasive outside its native habitat.  More broadly "weed" occasionally is applied pejoratively to species outside the plant kingdom, species that can survive in diverse environments and reproduce quickly; in this sense it has even been applied to humans. Closterovirus, also known as beet yellows viral group, is a genus of viruses, in the family Closteroviridae.  Plants serve as natural hosts.  There are currently 11 species in this genus.  Diseases associated with this genus include: yellowing and necrosis, particularly affecting the phloem.  This genus has a probably worldwide distribution and includes among other viral species the "Beet yellows virus" (the type species) and "Citrus tristeza virus", rather economically important plant diseases.  At least some species require vectors such as aphids or mealybugs for their transmission from plant to plant. Purshia glandulosa is a species of flowering plant in the rose family known by the common names antelope bitterbrush, desert bitterbrush, Mojave antelope brush.
Answer: Purshia