Question: Which plant genus is part of a family with a longer name, Morning glory or Rothmannia?

Context:
Ipomoea indica
Ipomoea indica is a species of flowering plant in the family Convolvulaceae, known by several common names, including blue morning glory, oceanblue morning glory, koali awa, and blue dawn flower.
Ipomoea wrightii
Ipomea wrightii, or Wright's morning glory, is a species of morning glory.
It is generally described as an annual, perennial vine or forb or herb.
 Wright's morning glory is not native to the United States and is considered as an invasive species.
 It is found growing in the Southeastern part of the United States.
Rothmannia
Rothmannia is a genus of flowering plants in the Rubiaceae family.
 It was described in 1776 and is named for Göran Rothman (1739–1778) by Thunberg – both were pupils of Linnaeus.
 The genus has a wide distribution area and is found tropical and southern Africa, western Indian Ocean, southern China to Indo-China and New Guinea.
Ipomoea carnea
Ipomoea carnea, the pink morning glory, is a species of morning glory.
 This flowering plant has heart-shaped leaves that are a rich green and 6 – long.
 It can be easily grown from seeds which are toxic and it can be hazardous to cattle; the toxicity is related to the swainsonine produced by endophytes and to bioaccumulation of selenium species in leaves but mostly in seeds
Bonamia grandiflora
Bonamia grandiflora is a rare species of flowering plant in the morning glory family known by the common names Florida lady's nightcap, Florida bonamia, and scrub morning glory.
 It is endemic to Central Florida, where there are about 100 known populations remaining, many of which are within the bounds of the Ocala National Forest.
 The plant has declined in recent decades primarily due to the development of its habitat, which is being converted to urban zones and citrus groves.
 This is the primary reason that the plant was federally listed as a threatened species in 1987.
Convolvulus cantabrica
Convolvulus cantabrica, common name Cantabrican morning glory or dwarf morning glory, is a herbaceous perennial plant belonging to the genus "Convolvulus" of the Convolvulaceae family.
Ipomoea coccinea
Ipomoea coccinea is a flowering plant in the family Convolvulaceae known by several common names including red morning glory, redstar and (ambiguously) Mexican morning glory.
Morning glory
Morning glory (also written as morning-glory) is the common name for over 1,000 species of flowering plants in the family Convolvulaceae, whose current taxonomy and systematics are in flux.
 Morning glory species belong to many genera, some of which are:
Ipomoea sagittata
Ipomoea sagittata, commonly called the saltmarsh morning glory, is a species of flowering plant in the morning glory family.
 It is native to the Caribbean, Mexico, and the Southeastern United States where it is found in coastal areas.
 Its natural habitats are thickets on barrier islands, the edges of salt marshes, and in hammocks.
Ipomoea aquatica
Ipomoea aquatica is a semiaquatic, tropical plant grown as a vegetable for its tender shoots and leaves.
 It is found throughout the tropical and subtropical regions of the world, although it is not known where it originated.
 This plant is known in English as water spinach, river spinach, water morning glory, water convolvulus, or by the more ambiguous names Chinese spinach, Chinese Watercress, Chinese convolvulus, swamp cabbage or kangkong in Southeast Asia.
 Occasionally, it has also been mistakenly called "kale" in English, although kale is a strain of mustard belonging to the species "Brassica oleracea" and is completely unrelated to water spinach, which is a species of morning glory.
 It is known as "phak bung" in Thai and Laotian, "eng chai" in Teochew and Hokkien, "ong choy" (蕹菜) in Cantonese, "kongxincai" (空心菜) in Mandarin Chinese, "rau muống" in Vietnamese, "kangkong" in Tagalog, "kangkung" in Indonesian and Malay, "gazun" in Myanmar, "trokuon" (ត្រកួន) in Khmer, "kolmou xak" in Assamese,"வள்ளல்" (vallal) in Tamil, "kalmi saag" in Hindi, "kalmi shak" in Bengali, "Thooti Koora" in Telugu, "Kalama Saga" in Odia, "hayoyo" in Ghana.
 In Suriname (South-America) it is known as "dagoeblad" or "dagublad".

Answer: Morning glory