Question: Which of the following is a type of cacti known to grow in Brazil: Piper or Discocactus?
Context: Air 500 Limited was a Canadian airline.  Founded in 1985 by Dennis Chadala, former Captain, director of marketing and assistant to Carl Millard, of the defunct Millardair.  The company commenced operations with 1 Super Beech 18 Model E, registered C-FTAE that was purchased from Bradley First Air where it had retired from flying the dew line in Northern Canada.  The Beech18 was originally purchased new by Timmins Aviation.  The founder had extensive knowledge of the emergency freight business and the operation of DC3s, Super DCs and DC4 aircraft due to his position within the inner circle at Millardair.  Dennis Chadala created Air 500 Limited on a shoe string, without financing and was the first airline to receive licensing and an operating certificate at Toronto's Pearson International Airport following deregulation of the aviation industry in Canada in 1985.  The airline grew rapidly adding an aircraft at the pace of 1 every six months.  By 1989 it had acquired almost all of the business flying ad hock charter out of Toronto for Chrysler, Ford, GM and many others formerly serviced by his former place of employment at Millardair.  The young owner's extensive knowledge of this niche area of aviation enabled him to expand rapidly and capture that market segment.  At the time, Air 500 was an exceptional success story operating 3 Super Beech 18 aircraft, 2 Cessna 310s, 1 DC3, 1 Super DC(C117), 1 Piper Cheyenne and 1 Mitsubishi MU2 Marquise.  In the early nineties, the fleet continued to grow adding 2 more Mitsubishi MU2 aircraft, 2 Citation 500 business jets and 1 Citation 2 business jet.  In 1995 the airport was privatized and came under the direction and control of the GTAA (Greater Toronto Airport Authority) and Dennis Chadala simultaneously acquired Hangar #7, the newest hangar facility at the north end of the Pearson Airport off Derry Road with 40 years remaining on the current land lease.  Air 500 had contracts in the courier industry, Air Ambulance Services and Aircraft Management as well as a base of operations at the Esso Avitat in Ottawa where 2 Mitsubishi Marquise MU2 aircraft were stationed.  One was flying an exclusive long term contract for Nordion (formerly Atomic Energy of Canada) flying radio active isotopes to numerous destinations in the United States for medical purposes as a well a designated charter aircraft.  Hangar #7 was large enough to lease out one half the facility to Air 500 Limited and the other half to Execaire/Innotech Aviation and they remained tenants of the hangar owned by Dennis Chadala until November 1998, at which time Execaire/Innotech owned by the IMP Group out of Halifax Nova Scotia struct a deal with Dennis Chadala to purchase his hangar facility, all his aircraft and the operating airline Air 500 Limited.  Dennis Chadala stayed on with the company during a short transition period that ended in February 1999.  Air 500 was amalgamated into Execaire and became part of that operating group taking advantage of the synergies available to them. Discocactus is a genus of tropical cacti.  The name comes from the ancient Greek "diskos " (=disc) because of its shape.  "Discocactus" plants are endemic to southern Brazil, eastern Bolivia, and northern Paraguay.  These species are in the risk of extinction in the wild. Ariocarpus retusus is a species of cactus, from the genus "Ariocarpus", found mainly in Mexico.  It is one of the largest and fastest-growing species of this genus, known for its slow growth.  Despite its slow growth, often taking 10 years to reach flowering age, the "retusus" is a desirable cactus for cultivation, having attractive flowers and an interesting form.  It is also one of the easiest cacti to grow from the genus. The Best of Billie (originally known as "The Very Best of Billie Piper") is a compilation album by British pop singer Billie Piper.  It was released by EMI Gold on 8 August 2005 following Piper's high-profile return to the public eye in "Doctor Who".  The compilation contained Piper's single releases as well as B-sides.  The compilation was released as a budget album in the United Kingdom, and therefore was ineligible to chart.  However it did manage to peak at Number 41 on the UK Budget Albums Chart. Charmed is an American television series created by Constance M. Burge and produced by Aaron Spelling and his production company Spelling Television, with Brad Kern serving as showrunner.  The series was originally broadcast by The WB for eight seasons from October 7, 1998, until May 21, 2006.  The series narrative follows a trio of sisters, known as The Charmed Ones, the most powerful good witches of all time, who use their combined "Power of Three" to protect innocent lives from evil beings such as demons and warlocks.  Each sister possesses unique magical powers that grow and evolve, while they attempt to maintain normal lives in modern-day San Francisco.  Keeping their supernatural identities separate and secret from their ordinary lives often becomes a challenge for them, with the exposure of magic having far-reaching consequences on their various relationships and resulting in a number of police and FBI investigations throughout the series.  The series initially focuses on the three Halliwell sisters, Prue (Shannen Doherty), Piper (Holly Marie Combs) and Phoebe (Alyssa Milano).  However, following Prue's death in the third-season finale, their long-lost half sister Paige Matthews (Rose McGowan) assumes her place within the "Power of Three" from season four onwards. "Charmed" is an American television series that was originally broadcast by The WB for eight seasons from October 7, 1998, until May 21, 2006.  The series narrative follows a trio of sisters, known as The Charmed Ones, the most powerful good witches of all time, who use their combine Power of Three to protect innocent lives from evil beings such as demons and warlocks.  Each sister possesses unique magical powers that grow and evolve, while they attempt to maintain normal lives in modern-day San Francisco.  The main characters of the first three seasons were Prue (Shannen Doherty), Piper (Holly Marie Combs) and Phoebe Halliwell (Alyssa Milano).  After Doherty departed from the series in 2001, resulting in her character's death, she was replaced by Rose McGowan as the long-lost younger half-sister Paige Matthews from the fourth season onwards.  The following list only contains characters that appeared in five or more episodes. Brasilicereus is a genus of cacti known only from Brazil and comprising 2 species. Piper, the pepper plants or pepper vines (a term used for certain "Clematis" in older times), are an economically and ecologically important genus in the family Piperaceae. Platypodium elegans or the graceful platypodium is a large leguminous tree found in the Neotropics that forms part of the forest canopy.  It was first described by Julius Rudolph Theodor Vogel in 1837 and is the type species of the genus.  The tree has been known to grow up to 30 metres in height and have a trunk with a diameter up to 1 m at breast height.  Its trunk has large holes in it, sometimes making it possible to see through the trunk.  The holes provide a habitat for giant damselflies and other insects both when alive and once the tree has died and fallen over.  It has compound leaves each of which is made up of 10–20 leaflets.  Three new chemical compounds have been isolated from the leaves and they form part of the diet of several monkeys and the squirrel "Sciurus ingrami".  In Panama it flowers from April to June, the flowers contain only four ovules, but normally only one of these reaches maturity forming a winged seed pod around 10 cm long and weighing 2 g.  During the dry season around a year after the flowers are fertilised, the seeds are dispersed by the wind and the tree loses it leaves.  The seeds are eaten by agoutis and by bruchid beetle larvae.  The majority of seedlings are killed by damping off fungi in the first few months of growth, with seedlings that grow nearer the parent trees being more likely to die.  The seedlings are relatively unable to survive in deep shade compared to other species in the same habitat.  Various epiphytes are known to grow on "P. elegans" with the cactus "Epiphyllum phyllanthus" being the most abundant in Panama.  Despite having holes in its trunk which should encourage debris and seeds to collect, hemiepiphytes are relatively uncommon, meaning that animals are not attracted to it to feed and then defecate.  It has no known uses in traditional medicine and although it can be used for timber, the wood is of poor quality. Schlumbergera is a small genus of cacti with six species found in the coastal mountains of south-eastern Brazil.  Plants grow on trees or rocks in habitats that are generally shady with high humidity, and can be quite different in appearance from their desert-dwelling cousins.  Most species of "Schlumbergera" have stems which resemble leaf-like pads joined one to the other and flowers which appear from areoles at the joints and tips of the stems.  Two species have cylindrical stems more similar to other cacti.  In Brazil, the genus is referred to as "Flor de Maio " (May flower), reflecting the period in which they flower in the Southern Hemisphere.
Answer: Discocactus