Question: Which flowering plant is native to Central America, Helictotrichon or Odontonema?
Context: Odontonema strictum, the mottled toothedthread, the Cardinal’s guard, or the firespike, is a species of plant in the family Acanthaceae which is endemic to Mexico, but has been introduced to Florida, Central America, South America, the West Indies, and several Pacific Islands. Aeschynomene americana is a species of flowering plant in the legume family known by many common names, including shyleaf, forage aeschynomene, American joint vetch (United States and Australia), thornless mimosa (Sri Lanka), bastard sensitive plant (Jamaica), pega pega, pega ropa, antejuela, ronte, cujicillo, and dormilonga (Latin America).  It is native to Central America, parts of South America, the West Indies, and Florida. Helictotrichon sempervirens, or blue oat grass, is a species of flowering plant in the Poaceae family of true grasses, native to central and southwest European grasslands.  It is a bunchgrass often used as an ornamental grass in garden design and landscaping. Heimia salicifolia is a species of flowering plant in the Loosestrife family, Lythraceae.  It is native to the Americas, ranging from the southwestern United States (Texas and New Mexico) through Mexico and Central America to Argentina.  Common names include shrubby yellowcrest, sinicuichi, sun opener, willow-leaf heimia, sini.  The plant has been used for shamanic purposes by native peoples in Central America and Mexico. Ludwigia octovalvis is a species of flowering plant in the evening primrose family known by the common name Mexican primrose-willow.  Its native distribution is unclear, but can be found in Central America, Australia, South-East Asia, the Middle East, the Central-West African regions and spreads easily to become naturalized.  It is also cultivated as an aquatic plant.  The plant is known for its anti-ageing properties.  The species is sometimes regarded as an invasive species and is classified by IUCN as of Least Concern with stable populations.  An adult plant is one meter tall on average but is able to grow taller.  and spreads to form mats on the mud, rooting at nodes in contact with the substrate, or floats ascending in the water.  Its flowers are yellow in appearance.  They are made up of green and red stems.  They yield small capsular fruits containing many minute seeds. Odontonema, the toothedthreads, is a genus of flowering plants in the bear's breeches family, Acanthaceae.  It is native to Central America. Diodella teres is a species of flowering plant in the coffee family known by the common names poorjoe and rough buttonweed.  This annual plant is native to Mexico, Central America, South America, the West Indies and the southern of the United States from California to Florida as well as much of the central and northeastern United States from Kansas to Michigan to Massachusetts.  The species is also naturalized in the Netherlands, the Canary Islands, Western Africa, Angola, China, Japan and Korea, India, and Madagascar. Helictotrichon pubescens, downy oat-grass or downy alpine oatgrass, also known by its synonym "Avenula pubescens", is a species of flowering plant in the Poaceae family.  It is native to Europe and Asia.  It can also be found in such US states as Connecticut, Delaware, Minnesota, New Jersey and Vermont, and in Canadian provinces such as Alberta, Manitoba, Ontario, Quebec, and Saskatchewan. Helictotrichon (alpine oatgrass) is a genus of perennial flowering plants in the grass family. .  Genus name comes from the Greek heliktos meaning twisted and trichos meaning spine, referring to the shape of the awn. Claytonia perfoliata (Indian lettuce, spring beauty, winter purslane, or miner's lettuce ; syn.  "Montia perfoliata") is a flowering plant in the family Montiaceae.  It is a fleshy, herbaceous annual plant native to the western mountain and coastal regions of North America from southernmost Alaska and central British Columbia south to Central America, but most common in California in the Sacramento and northern San Joaquin valleys.
Answer: Odontonema