I. M. Johnston, was a United States botanist. He studied at Pomona College in Claremont, California and at Harvard University. His plant collections are housed in the Rancho Santa Ana Botanic Garden, in Claremont, and also in the Gray Herbarium of Harvard University.
John Thomas Howell was an American botanist and taxonomist. He became an expert of Eriogonum (buckwheat) species, which are widely represented in the native California flora.
Harmsia is a genus of flowering plants belonging to the family Malvaceae.
Heeria is a monotypic genus of flowering plants belonging to the family Anacardiaceae. It only contains one species, Heeria argentea(Thunb.) Meisn.
Henslowia is a genus of flowering plants belonging to the family Santalaceae.
Hornea is a monotypic genus of flowering plants belonging to the family Sapindaceae. It only contains one species, Hornea mauritianaBaker
Delpinophytum is a monotypic genus of flowering plants belonging to the family Brassicaceae, with one species,Delpinophytum patagonicum(Speg.) Speg.
Haussknechtia is a monotypic genus of flowering plants belonging to the family Apiaceae. It only contains one species, Haussknechtia elymaiticaBoiss. It is commonly known as johour or white celery in Iran.
Heldreichia is a monotypic genus of flowering plants belonging to the family Brassicaceae. It only contains one species, Heldreichia bupleurifoliaBoiss.
Ellisiophyllum is a monotypic genus of flowering plants belonging to the family Plantaginaceae. It contains just 1 species, Ellisiophyllum pinnatum(Wall. ex Benth.) Makino
Dintera is a monotypic genus of flowering plants belonging to the family Plantaginaceae. It contains just one species, Dintera pterocaulisStapf, which comes from Namibia.
Irvingbaileya is a monotypic genus of flowering plants belonging to the family Stemonuraceae. It is a dioecious tree.
Hochreutinera is a genus of flowering plants belonging to the family Malvaceae.
Howelliella is a monotypic genus of flowering plants belonging to the family Plantaginaceae. It only contains one species, Howelliella ovata.
Hullettia is a genus of flowering plants belonging to the family Moraceae.
Hectorella is a genus of flowering plants belonging to the family Montiaceae. It is monotypic, being represented by the single species Hectorella caespitosa. It is native to New Zealand.
Hiernia is a monotypic genus of flowering plants belonging to the family Orobanchaceae. It only contains one species, Hiernia angolensisS.Moore
Guilfoylia is a monotypic genus of flowering plants belonging to the family Surianaceae. The only species is Guilfoylia monostylis.
Hellmuthia is a monotypic genus of flowering plants belonging to the family Cyperaceae. The only species is Hellmuthia membranacea.
Gambelia is a genus of flowering plants in the Plantaginaceae family. It is also in the Antirrhineae tribe, within the family.
