He was a member of the"Scientific Corps" of Commodore Charles Wilkes' United States' Exploring Expedlition (1838 - 1842), which visited New South Wales in 1839. He collected mostly in the Sydney and Hunter River districts, and the specimens collected by the expedition were described in Asa Gray's work on the botany of the Expedition (New York, 1857).
"The ferns and allied orders were worked up by Mr. Brackenridge. With the exception of a few presentation copies of Mr. Brackenridge's portion of this work which happened to have been sent off to Europe, the whole stock was burnt in the fire which destroyed the storehouse, so that it has now become extremely rare," (Seemann, Fl. Vitiensis, vii).
Brackenridge was attached to the U.S. Ship Vincennes as “Assistant Botanist," apparently serving the whole of the cruise. William Rich "joined the Peacock at Callao and the Vincennes at San Francisco, as "Botanist," and Brackenridge was probably subordinate to him. They worked together. Mr. Brackenridge is sometimes also called “Horticulturist." The genus Brackenridgea , Gray, (Ochnaceae) from Fiji (there is also an Australian species) commemorates him.
Brackenridgea nitida A.Gray
Brackenridgea australiana F.Muell. ( as `Brackenridgia' )
Brackenridgea nitida subsp. australiana (F.Muell.) Kanis
Cyathea brackenridgei Mett.
Source: Maiden, J.H. (1908) Records of Australian botanists- (a) General, (b) New South Wales. Journal and Proceedings of the Royal Society of New South Wales for 1908 . 42:60-132