Nemophila is a genus endemic to North America (USA and further south to Baja California) and counts about 11-18 annual species, depending on species delimitation (Helfgott & Simpson 2001, Mabberley 2008, Barr 2014). It is predominantly dispersed in western North America with two species occurring disjunct in the southeastern USA. The latter are not sister to the western taxa and thus may have resulted from independent dispersal or vicariant events (Helfgott & Simpson 2001).
Two species are commonly cultivated as garden ornamentals and both have been recorded as escapes in Belgium.
1 Tip of petal with a large, purple spot === Nemophila maculata
Tip of petal unspotted === N. menziesii
Barr C.M. (2014) Phylogenetic Relationships and Crossing Data Reveal a New Species of Nemophila (Boraginaceae). Madroño 61(3): 308-315. [available online at: https://www.biodiversitylibrary.org/page/53452930#page/326/mode/1up]
Chandler H.P. (1902) A revision of the genus Nemophila. Botanical Gazette 34: 194–215. [available online at: https://www.biodiversitylibrary.org/item/91645#page/257/mode/1up]
Chandler H.P. (1907) Notes on two California Nemophilas. Botanical Gazette 44: 381–382. [available online at: https://www.biodiversitylibrary.org/item/90333#page/485/mode/1up]
Chittenden R.J. & Turrill W.B. (1926) Taxonomic and genetical notes on some species of Nemophila. Bulletin of Miscellaneous Information (Royal Gardens, Kew) 1: 1–12. [available online at: https://www.jstor.org/stable/4114316]
Constance L. (1941) The genus Nemophila Nutt. University of California Publications in Botany 19: 341–345.
Eastwood A. (1901) Some small-flowered Species of Nemophila from the Pacific Coast. Bulletin of the Torrey Botanical Club 28: 137–160. [available online at: https://www.biodiversitylibrary.org/item/8006#page/172/mode/1up]
Eastwood A. (1902) New species of Nemophila from the Pacific Coast. Bulletin of the Torrey Botanical Club 29: 471–474. [available online at: https://www.biodiversitylibrary.org/item/8007#page/544/mode/1up]
Helfgott D.M. (2000) Evolution and molecular systematics of Nemophila Nutt. (Hydrophyllaceae) and the woody Bencomia alliance (Rosaceae). Ph.D. Dissertation. The University of Texas at Austin, Austin, TX.
Helfgott D.M. & Simpson B.B. (2001) Phylogenetics of Nemophila using molecular and morphological data. [available online at: http://2001.botanyconference.org/section12/abstracts/282.shtml]
Mabberley D.J. (2008) Mabberley’s plant-book (3th ed.). Cambridge University Press, Cambridge: XVIII + 1021 p.
Simpson B.B., Helfgott D.M. & Neff J.L. (2001) A new cryptic species of Nemophila (Hydrophyllaceae) from Texas and the lectotypification of N. phacelioides Nuttall. Lundellia 3: 30–36. [available online at: http://w3.biosci.utexas.edu/prc/pdfs/Simpson_Lundellia04.pdf]