One plant genus and 14 plant species named after Francis Guthrie, who first made the graph-theoretical Four-Color Conjecture

In 1852, the English law student Francis Guthrie at the University College of London conjectured that four colors would suffice to color any map, such, that border-sharing regions never come to share the same color [1-3]. The Four-Color Problem, or Four-Color Conjecture, turned into a theorem, when it was proven in 1976 by Kenneth Appel and Wolfgang Haken—a computer-assisted proof, triggering further work in theorem-proving software and strategies.  

Francis Guthrie (1831-1899) developed a strong interest in mathematics and botany. In 1861, Guthrie left England for the Cape Colony, now part of South Africa, where he took up the chair of Mathematics at the Graaff-Reinet College and, in 1878, at the South African College (Zuid Afrikaansche Athenaeum), which became the University of Cape Town in 1918 [2]: Besides mathematics, Guthrie taught botany; inspiring Harry Bolus (1834-1911), who later became a celebrated botanist and illustrator. Honoring his teacher, Bolus named a genus in the plant family Achariaceae after Guthrie: Guthriea Bolus, including the flowering plant Guthriea capensis [4].

Bolus also named plant species after Guthrie. For example, Satyrium guthriei Bolus (1893) in the family Orchidaceae, Gladiolus guthriei Bolus (1917) in the Iris family and Indigofera guthriei Bolus in the family Fabaceae [2,4-6]. 

Keywords: mathematics, graph theory, history, botany, plant species, flowering plants, taxonomy.

References and more to explore
[1] J. J. O'Connor and E. F. Robertson: The four colour theorem. September 1996 [www-groups.dcs.st-and.ac.uk/~history/HistTopics/The_four_colour_theorem.html].
[2] Pieter Maritz and Sonja Mouton: Francis Guthrie: A Colourful Life. The Mathematical Intelligencer 2012, 34 (2), pp. 67-75. DOI: 10.1007/s00283-012-9307-y.
[3] Georges Gonthier: Formal Roof—The Four-Color Theorem. Notices of the AMS December 2008, 55 (11), 1382-1393. PDF: www.ams.org/notices/200811/tx081101382p.pdf.
[4] JSTOR PLANT SCIENCE: Guthriea capensis Bolus [plants.jstor.org/visual/nbgsld0001378], Satyrium Guthriei Bolus [plants.jstor.org/flora/floc014377], Indigofera guthriei Bolus [plants.jstor.org/specimen/nh0005500-0]. 
[5] Victoria Wilman: Gladiolus guthriei F. Bolus [www.plantzafrica.com/plantefg/gladiolusguthriei.htm].
[6] Red List of South African Plants: Indigofera guthriei Bolus [http://redlist.sanbi.org/species.php?species=357-204].