Ever since Marianne North’s sister, Janet Catherine Symonds, published a condensed version of Marianne’s journals, it has been claimed that one Genus and four species were named in her honour and for the last century, the claim has been repeated so often that it has become gospel. Unfortunately, it isn’t that simple, while the Genus name and one of the Species names are verifiably correct, there are problems with the remaining three that range from mis-transcribed to non-existent.
In Recollections of a Happy life, Janet Symonds states:
Her name has been given to five; four of which were first figured and introduced by her to European notice, viz-
Northea Seychellana
Nepenthes Northiana
Crinum Northianum
Areca Northiana
Kniphofia Northiana i
The 1st to 4th editions of the Gallery Guide, make reference to only one of the Species cited by Mrs Symonds, though it doesn’t explicitly state that it was named after Marianne:
565. Brisbane Botanic Gardens. – Palms in the foreground and avenue of Araucarias behind. The two tall palms are a species of Ptychosperma ; the dwarf one behind, Areca Northiana, Hill; with Kentia minor, F. Muell., on the right.ii
From the 5th edition of the guide onwards, the forward explicitly states that one Genus and three Species are named after her:
On her return from South America in 1885, Miss North at once commenced hanging the new paintings, which, including those from South Africa and Seychelles, are some two hundred in number. Among the latter was the “Capucin,” an imperfectly known tree. The drawing of the foliage and fruit brought by Miss North, with the flowers, which were subsequently sent at her request, enabled Sir Joseph Hooker to determine the tree to be a new genus, which he appropriately named Northea in honour of the artist. Miss North is also commemorated in Crinium Northianum, Baker, Kniphofia Northiana, Baker and Nepanthes Northiana, Hook. f.. the former of which was described from her drawings, – the highest compliment which could be paid to their scientific accuracy. iii
The fourth species, which was numbered 565 in the 1st to 4th editions of the guide, by the time of the 5th edition is re-numbered to 743, using exactly the same text as the original. At no point is there any confirmation that Areca Northiana is actually named in Marianne North’s honour. The only person to make this connection is Janet Symonds in Recollections.
The following is a summary of each claim…
Northia 
The accepted name for the genus of plants in the family Sapotaceae. The name was first published by Joseph Dalton Hooker, in Hooker’s Icones Plantarum (Sep 1884), in his description of Northia seychellana. The spelling was given as Northia on the plate, but the variant Northea was given in the text, probably due to a typographical error. Northia seychellana is the only species accepted in the genus and it is endemic to the Seychelles. A few other species were formerly included in Northia but have since been moved to Manilkara.
Nepenthes northiana
The accepted Species name Nepenthes northiana, or Miss North’s pitcher-plant, is a tropical pitcher plant endemic to Borneo. Marianne North was the first person to illustrate the species and so it is named in her honour.
Kniphofia northiana 
Kniphofia northiae
A misgiven name, referring to Kniphofia northiae. The species was named after Marianne North, but the name has been misgiven in the gallery for over a hundred years. It is one of the African torch lilies or poker plants. ‘Kniphofia northiae’ is the accepted species name, while ‘Kniphofia northiana’ has no standing.
Crinum northianum
This name is a synonym of Crinum asiaticum var. asiaticum. It is an evergreen perennial, producing a rosette of fleshy leaves ‘Crinum asiaticum’ is the accepted species name, while ‘Crinum northianum’ is only accepted as having been at some time, a former, sparsely used, reference to the species.
Areca northiana
Is an invalid name and the species being referred to is unknown. The name of the species is taken to have been proposed by Helmsley in the 1st edition of the Marianne North Gallery Catalogue (1882), although in reality, the entry for painting 565 (see above) merely attributes the name to Walter Hill of the Brisbane Botanic garden. If Hill did name the palm, he didn’t follow the appropriate naming conventions and publish a description. Indeed, there appears to be no paperwork in Hill’s collection referring to Areca northiana. The only evidence of Areca northiana therefore, is the gallery painting itself, where it is depicted as a dwarf palm growing behind two larger palms.
Dr Dowie of the James Cook University, Queensland, Australia, suggests that the palm may be a juvenile Dictyosperma album, or hurricane palm. There is a very old specimen of this, growing in the same location (as of December 2017) and this may be what was painted by Marianne in its juvenile state. The palm that was painted by Marianne North however, looks as if it has fibrous sheaths which do not occur with Dictyosperma. This may mean that the Dictyosperma which now occupies the area, is younger than Marianne’s visit, or that Marianne was confused about the features she was painting. Because of this, and failing any other information coming to light, it is likely that we will never know what species of palm Areca northiana was intended to be. Therefore it will just have to remain an unknown palm.
i Symonds, Mrs J. A. : Recollections Of A Happy Life, Vol. II, p. 337 : Macmillan and Co. : London : 1892
ii The Gallery of Marianne North’s Paintings, p. 103 : Spottiswoode & Co. : London : 1892. By the time of the fifth edition of the guide, the painting had been renumbered 743, and the entry is on page 113
iii “Biographical Notice of Marianne North” : p. ix. : Official Guide to the Marianne North Gallery : Sixth Edition : HM Stationary Office : London : 1914