Question: While Opuntia is from the genus of the cactus family, what genus is the Houttuynia?

full_context: Document 1: Opuntia alta: Opuntia alta is a cactus species in the "Opuntia" genus. It is a large plant, with some older specimens forming trees to 15 ft tall. It resembles "Opuntia lindheimeri", and immature specimens can be mistaken for that taxon. Mature O. alta plants form discrete trunks and have small fruits. Unlike O. lindheimeri, the flowers have pale stigmas.
Document 2: Opuntia cacanapa: Opuntia cacanapa is a cactus in the "Opuntia" genus. In the United States it is found on the South Texas Plains in Brewster County and adjacent counties to the southeast. It also occurs in nearby Mexico.
Document 3: Tetradium ruticarpum: Tetradium ruticarpum is a tree that comes from China and Korea. It was previously classified in the genus "Euodia" as "Euodia ruticarpa". The fruit is usually used, denoted sometimes as "fructus". It has a strong bitter taste, and is used in traditional Chinese medicine (TCM) and is a recognized herb in Kampo. Both the former genus name and the species name are often misspelled, and the plant usually appears in sources dealing with traditional Chinese medicine as ""Evodia(e) rutaecarpa"".
Document 4: Houttuynia: Houttuynia is a genus of two species in the Saururaceae native to Southeast Asia. One species, "H. cordata", is widely cultivated as a culinary herb. The genus was originally described in 1783 by Carl Peter Thunberg when he formally described "H. cordata" as the only species. It remained a monotypic genus until 2001 when Zheng Yin Zhu and Shi Liang Zhang discovered and described a second species native to China, "H. emeiensis".
Document 5: Hydrangea: Hydrangea ( ; common names hydrangea or hortensia) is a genus of 70–75 species of flowering plants native to southern and eastern Asia (China, Japan, Korea, the Himalayas, and Indonesia) and the Americas. By far the greatest species diversity is in eastern Asia, notably China, Japan, and Korea. Most are shrubs 1 to 3 meters tall, but some are small trees, and others lianas reaching up to 30 m by climbing up trees. They can be either deciduous or evergreen, though the widely cultivated temperate species are all deciduous.
Document 6: Kaempferia rotunda: Kaempferia rotunda is a plant species in the ginger family. It is native to China (Guangdong, Guangxi, Hainan, Taiwan, Yunnan), India, Nepal, Assam, Bangladesh, Indochina, and widely cultivated elsewhere. It is reportedly naturalized in Java, Malaysia and Costa Rica.
Document 7: Opuntia anahuacensis: Opuntia anahuacensis is a cactus species in the "Opuntia" genus and a member of the Opunitioideae. It grows along the Gulf Coast of Texas, and perhaps northern Mexico. The plants are short, perhaps 1- or 2-ft tall, but they are wide. Some thickets may be 20- to 40-ft across and composed of multiple plants. The fruit is purplish. The cladodes are uniquely shaped, obovate with a neck. The original description claimed the plants were yellowish green, but they may be green or rarely blue-green.
Document 8: Opuntia chlorotica: Opuntia chlorotica is a species of plant in the Cactaceae family. It is a species of prickly pear native to the southwestern United States and northern Mexico. Its common names include pancake prickly pear, flapjack prickly pear and dollarjoint prickly pear.
Document 9: Schlumbergera opuntioides: Schlumbergera opuntioides is a species of plant in the Cactaceae family. It is endemic to the coastal mountains of south-eastern Brazil where its natural habitats are humid forests and rocky areas. It is threatened by habitat loss. It is in the same genus as the popular house plant known as Christmas Cactus or Thanksgiving Cactus.
Document 10: Opuntia: Opuntia is a genus in the cactus family, Cactaceae.
Document 11: Emmenopterys henryi: Emmenopterys henryi is a species of flowering plant in the Rubiaceae family. It is found in the temperate parts of central and southern China and in Vietnam. It is a deciduous tree with opposite leaves and can attain heights of 45 m and grow to be 1000 years old. The epithet is named after the Irish botanist and sinologist Augustine Henry.
Document 12: Kaempferia galanga: Kaempferia galanga, commonly known as kencur, aromatic ginger, sand ginger, cutcherry, or resurrection lily, is a monocotyledonous plant in the ginger family, and one of four plants called galangal. It is found primarily in open areas in Indonesia, southern China, Taiwan, Cambodia, and India, but is also widely cultivated throughout Southeast Asia.
Document 13: Opuntia atrispina: Opuntia atrispina is a cactus species in the "Opuntia" genus. It has limited distribution in the United States. In Texas it can be found from near Uvalde to Del Rio/Langtry--a small strip of area just 50 miles long.
Document 14: Perilla frutescens: Perilla frutescens, commonly called perilla or Korean perilla, is a species of "Perilla" in the mint family Lamiaceae. It is an annual plant native to Southeast Asia and Indian highlands, and grown in the Korean peninsula, Southern China and India. Known as "deulkkae" (들깨 ) in Korean, the plant was introduced into Korea before the Unified Silla era, when it started to be widely cultivated.
Document 15: Opuntia aciculata: Opuntia aciculata, also called Chenille pricklypear, old man's whiskers, and cowboy’s red whiskers, is a perennial dicot and an attractive ornamental cactus native to Texas. It belongs to the genus "Opuntia" prickly pear cacti. It is also widespread in Nuevo Leon, Tamaulipas (northern Mexico).
ground_truth: two species in the Saururaceae