Primula involucrata or Primula munroi?

There has been confusion over the names P. involucrata and P. munroi for a long time and currently both names are used. So which is the correct name? The problem starts with Nathaniel Wallich, a Danish botanist who collected extensively in India, Nepal, West Hindustan and lower Burma. Wallich compiled a catalogue of plant specimens collected by him and others of the time and this is known as the “Wallich catalogue” and his specimens are housed at Kew and Calcutta (CAL), with duplicates at other herbaria.

Unfortunately all of Wallich’s names in the catalogue are considered “nomina nuda” and invalid, except where also published separately by him or other botanists. Wallich’s catalogue is available at the Biodiversity Heritage Library and catalogue number 7107 (compiled 1828) is P. involucrata. This would be the first published occurrence of the name, if it were not that it is invalid. The next validly published occurrence of Wallich’s P. involucrata is Duby in Prodromus [A. P. de Candolle], 8:42, 1844. Here a full description of P. involucrata was made and Wallich’s list number 7107 is referenced. This would then make Wallich’s species valid if not for one little problem.

In Sweet's Hortus Britannicus: Or a Catalogue of Plants Cultivated in the Gardens of Great Britain (1839) on page 562, there is a valid description for P. involucrata, citing that the plant is yellow flowered, involucred, from Egypt and figured in Curtis’s Botanical Magazine, t. 2842 (1828). The species described is not the same as Wallich's plant. Sweet's valid description predates the Duby publication and so the name P. involucrata was not available to be used by Duby and therefore P. involucrata (Duby) becomes a later homonym of P. involucrata (Sweet).

The next validly published description for Wallich’s species was P. munroi, made by Lindley in Edward’s Botanical Register, 33, t. 15 (1847). So P. munroi becomes the valid name for the species we are all so familiar with.

P. munroi subsp. yargongensis (L), P. munroi subsp. munroi (C), P. munroi subsp. schizocalyx (R)

There are two subspecies associated with Primula munroi: P. munroi Lindl. subsp. schizocalyx Balf.f. ex S.K.Basak & Maiti and P. munroi Lindl. subsp. yargongensis (Petitm.) D.G.Long. The subspecies schizocalyx is distinguished by its calyx which is split to the base and is only found in Northern Sikkim. The subspecies yargongensis was originally described as a distinct species with dark purple flowers from the Zamba La (Sichuan) which would distinguish it from P. munroi subsp. munroi which is white. However images from the wild of populations in the Eastern part of the range (Yunnan, Sichuan) and from the Western part of the range (Nepal, India), show that the flower color can vary from white to purple in both populations. The Flora of China gives the tube length as being marginally longer than the calyx in subspecies yargongensis, but it could be that this distinction varies and may not be enough to warrant subspecies status.