Question: Which has more species, Nicandra or Halesia?

Context paragraphs:
Nicandra: Nicandra is a monotypic genus of flowering plants in the nightshade family containing the single species Nicandra physalodes.  It is known by the common names apple-of-Peru and shoo-fly plant.  It is thought originally to have been native to Peru (known elsewhere as an introduced species and sometimes as a weed) and is found nowadays as a ruderal species in tropical, subtropical and, to a lesser extent, temperate areas all over the world.  It has also long been cultivated as an ornamental plant for its attractive flowers and curious fruits (the latter sometimes dried for use in floral design) and has been adopted into the traditional medicine of countries far-removed from its original home.

Halesia diptera: Halesia diptera, the two-wing silverbell or two-winged snowdrop tree, is a species in the family Styracaceae, native to the southeastern United States from South Carolina and Florida west to eastern Texas.  It is cultivated as an ornamental tree.

Halesia: Halesia, also known as silverbell or snowdrop tree, is a small genus of four or five species of deciduous large shrubs or small trees in the family Styracaceae.

Halesia tetraptera: Halesia tetraptera, commonly known as the common silverbell or mountain silverbell (or Carolina silverbell; syn.  "Halesia carolina" auct.  non L.), is a species in the family Styracaceae, native to the southeastern United States.  It is cultivated as an ornamental tree.

Halesia monticola: Halesia (tetraptera var.)  monticola, or mountain silverbell, was originally included in "H. carolina", but was identified first as a subspecies by Rehder in 1914, then as a species by Sargent in 1921.  More recently, some authoritative sources regard it only as a subspecies or variety, while other authoritative sources regard it as a species, as it is treated here.

Halesia carolina: Halesia carolina, commonly called Carolina silverbell or little silverbell, is a species of flowering plant in the family Styracaceae, native to the southeastern United States.

Halesia macgregorii: Halesia macgregorii is a species of flowering plant in the family Styracaceae.  It is endemic to southeastern China, where it grows at moderate altitudes of 700–1,200 m.  It is threatened by habitat loss.  Recent genetic evidence suggests it is probably more closely related to the genus "Rehderodendron" than to other species of "Halesia"; it may be transferred to that genus in the future.

Supporting paragraphs: Nicandra Halesia
Answer: Halesia