Question: Layia and Ptelea are genus' of what species?

Context paragraphs:
Layia: Layia is a genus of flowering plants in the daisy family known generally as tidy tips, native to western North America.  Several are California endemics.

Ptelea: Ptelea is a genus of flowering plants in the citrus family, Rutaceae.  The name, of Greek derivation, is the classical name of the elm tree.  Carl Linnaeus used that word for this genus because of the resemblance of its fruit to that of the elm.  Members of the genus are commonly known as hoptrees.

Pteleopsis myrtifolia: Pteleopsis myrtifolia (M.A.Lawson) Engl.  & Diels ('Ptelea' = elm, 'opsis' = resembling, 'myrtifolia' = leaves like those of the myrtle) is one of some 10 African species in this genus in the family of Combretaceae.  It is the only "Pteleopsis" species to occur in Southern Africa.  Its flowers are strongly scented and perceived by humans to be either 'honey-like' or 'cloying' or even 'stinky'.  The timber is red, hard and durable, and used for furniture and construction.

Supporting paragraphs: Layia Ptelea
Answer: flowering plants