Try to make your search as simple as possible:
Hexaglottis will find all items including that sequence of letters.
Search results for "Hexaglottis":
"Hexaglottis lewisiae" - Moraea lewisiae
"Hexaglottis longifolia" - Moraea longifolia
"Hexaglottis sp nov s.w. Cape" - Moraea sp. unident. sw Cape
"Hexaglottis virgata" - Moraea virgata