Diels, L. 1912–1913. Plantae Chinenses Forrestianae: Catalogue of all the plants collected by George Forrest during his first exploration of Yunnan and Eastern Tibet in the years 1904, 1905, 1906. Notes Roy. Bot. Gard. Edinburgh 7: 1–410. [Species and infraspecific taxa.], opus utique oppr. prop.

George Forrest (1873–1932) was a legendary plant collector famous for his seven expeditions to southwestern China, with a total of over 31,000 gatherings and discovering over 1000 new species. The collections during his first expedition to “Yunnan and Eastern Tibet in the years 1904, 1905, 1906” were studied by a number of researchers, and the results, including many novelties, were published in a series of papers on different genera and families entitled “Plantae Chinenses Forrestianae”, starting in December 1911 (Focke in Notes Roy. Bot. Gard. Edinburgh 5: 65–70. 1911) and continuing until March 1913 (Bonati in Notes Roy. Bot. Gard. Edinburgh 8: 37–45. 1913). In addition to the taxonomic papers, a catalogue was published listing all the collections. This had a Preface by George Forrest and a list of 20 botanists who had co‐operated in naming the plants in the list, but the Catalogue itself was prepared by Louis Diels (in Notes Roy. Bot. Gard. Edinburgh 7: 1–410. 1912–1913), and generally served as a conclusion incorporating the results of the taxonomic studies. The catalogue is arranged numerically according to Forrest's collection numbers, with each entry beginning with the collection number, followed by the identification by a specialist, and then by the collection information fully copied from the field label. There are also two indices, a “Catalogue of the Species arranged in Natural Orders” (pages 299–333) and a “Catalogue of the Species arranged in Alphabetical Order” (pages 334–410). Pages 1–80 are dated: Jul 1912; 81–160: Sep 1912; 161–240: Oct 1912; 241–320: Dec 1912; and 321–410: Oct. 1913.

A typical entry in the main part of the catalogue (pages 5–298) reads “3836. Swertia macrosperma, C. B. Clarke. Plant of 1 to 2 ft. Flowers pale blue. Open mountain pastureland on the eastern flank of the Tali Range. Lat. 25°40′ N. Alt. 10,000 to 11,000 ft. August 1906. W. Yunnan, China” (Diels, l.c.: 196). As shown in the entry, the collection information generally contains the descriptions of some morphological features (mainly height or habit and flower color, sometimes only height or flower color, and sometimes including some more details of floral and/or other features; see below), and this is the source of the problems with which we are dealing in this proposal. There are many names listed in Diels (l.c.) that had not previously been published, most of which were of new taxa that awaited formal descriptions. Later researchers generally considered these names to be nomina nuda, but some tended to believe that the associated morphological descriptions, although part of the collection information, technically validated these names (Art. 38.1(a) of the ICN; Turland & al. in Regnum Veg. 159. 2018).

We located 49 names in Diels (l.c.) presenting such problems. In 20 of the cases, the names were accompanied by a typical description as shown above. In 7 cases, the names were only accompanied by descriptions of height or flower color. In the other 22 cases, however, the names were accompanied by relatively detailed descriptions of floral features and even some other morphological features. For example, Aster pycnophyllus Franch. ex Diels (l.c.: 199) was accompanied by the description of “Plant of 1½ to 2 ft. Ray florets bright purplish‐blue, disc florets orange‐yellow”, and Cirrhopetalum amplifolium Rolfe ex Diels (l.c.: 66) was accompanied by both “Erect plant (epiphyte) of 12 to 15 inches” and “Foliage one solitary leaf, thick, fleshy, and with a pseudo‐bulb. Flowers a pale yellowish‐pink, veined deep purple‐lake.” Among the 49 names, 36 were formally described later, with 34 using the same names as in Diels (l.c.) and 2 being raised from varietal rank to that of species. These include 23 names republished in the series “Plantae Chinenses Forrestianae” the following year (in Notes Roy. Bot. Gard. Edinburgh 8: 1–45. Mar 1913). All but two of these have been considered as the first valid publication of what were considered nomina nuda in Diels (l.c.) (e.g., Editorial Committee of FRPS, Fl. Reipubl. Popularis Sin. 1959–2004; Wu, Fl. Yunnan. 1977–2010; Wu & al., Fl. China. 1994–2013). The exceptions were Kobresia capillifolia (Decne.) C.B. Clarke var. condensata Kük. (in Notes Roy. Bot. Gard. Edinburgh 8: 9. 1913; as ‘Cobresia’) and Rhododendron platyphyllum Balf. f. & W.W. Sm. (in Notes Roy. Bot. Gard. Edinburgh 9: 259. 1916), which were accepted to have been validly published in Diels (l.c.) (Table 1).

As to the other 13 names that have never been republished, Doronicum yunnanense Franch. ex Diels (l.c.: 151) and Gentiana robustior H.M. Burkill ex Diels (l.c.: 196) are currently accepted as validly published but treated as synonyms (Table 1); 5 names are cited as nomina nuda (e.g., Editorial Committee of FRPS, l.c.; Wu, l.c.; Wu & al., l.c.); and 6 seem to have been generally overlooked.

In addition, there are five new combinations and one replacement name that were validly published in Diels (l.c) (Table 2). Three of these names: Anaphalis bicolor Diels (l.c.: 48), A. delavayi (Franch.) Diels (l.c.: 205), and Elsholtzia communis (Collett & Hemsl.) Diels (l.c.: 47), are currently accepted. [Although A. bicolor has traditionally been considered a combination based on Gnaphalium bicolor Franch., it is actually a replacement name, because Franchet's name is a later homonym of G. bicolor (Lindl.) Sch. Bip. (in Bot. Zeitung (Berlin) 3: 171. 1845) and thus illegitimate.] The other three new combinations: Didissandra lanuginosa var. lancifolia (Franch.) Diels (l.c.: 43), Sedum linearifolium var. balfourii (Raym.‐Hamet) Raym.‐Hamet ex. Diels (l.c.: 399), and S. linearifolium var. forrestii (Raym.‐Hamet) Raym.‐Hamet ex Diels (l.c.: 399), appear to have been overlooked in all later taxonomic studies.

If the ICN (Turland & al., l.c.) is strictly followed, the 22 names accompanied by relatively detailed descriptions in Diels (l.c.) have undoubtedly met the requirement of Art. 38.1(a) and need to be accepted as validly published. However, only three of them are currently accepted as validly published in Diels (l.c.), viz., Doronicum yunnanense (Diels, l.c.: 151), Gentiana robustior (Diels, l.c.: 196), and Rhododendron cephalanthum var. platyphyllum (Diels, l.c.: 211) (Table 1). Sixteen names have been considered validly published after Diels (l.c.). Their authorships will first need to be changed and attributed to “Diels”. In addition, five of them will potentially have the problem of incongruent typification and even of species delimitation because when republished the names were not based on the same gatherings as in Diels (l.c.). The remaining three names have been overlooked by later researchers. Their identities will require careful examinations.

For the 27 names with typical or less detailed descriptions, they may have to be submitted for binding decisions under Art. 38.4 to assess whether the associated descriptive statements satisfy the requirement of Art. 38.1(a) for valid publication. Since the descriptive material must be evaluated individually, a binding decision would have to be requested for every problematic case. Moreover, similar nomenclatural disruptions will occur if the names are ratified as validly published in Diels (l.c.). In the case that they are all accepted as validly published in Diels (l.c.), 19 names, which are currently considered validly published after Diels (l.c.), will need to change their authorships, and 7 of them will further have the potential problems of incongruent typification (and species delimitation). In particular, Ceropegia balfouriana Schltr. ex Diels (l.c. Sep 1912: 107) will threaten the currently accepted C. mairei (H. Lév.) H. Huber, which is based on Aristolochia mairei H. Lév. (in Bull. Géogr. Bot. 22: 228. Oct 1912), and Melampyrum chinense Dahl ex Diels (l.c.: 243) will threaten M. klebelsbergianum Soo (in J. Bot. 65: 144. 1927).

Suppressing the work of Diels (l.c.) seems to be a good solution to these problems. It avoids the potential nomenclatural disruptions and the need for an inordinate number of requests for binding decisions as described above. In addition, suppression will make unavailable any problematic names that we have failed to detect. In this study, we tried our best and located 49 problematic cases, but there may still be several names that we overlooked. It is highly probable that these names are being treated as nomina nuda or have just generally been overlooked, in view of their absence from major databases like IPNI and Tropicos. If Diels (l.c.) is not suppressed, they may pose new threats to nomenclatural stability or, at least, require additional requests for binding decisions.

Suppressing Diels (l.c.) will make the four currently accepted names (Table 1) and five new combinations and one replacement name (Table 2) not validly published (Art. 34.1), but, as outlined in Tables 1 and 2, this will have no significant disadvantages for current taxonomy and nomenclature.

In conclusion, after weighting the pros and cons, we considered that suppressing Diels (l.c.) is a desirable solution to the long‐term controversy over the valid publication of many names listed in the work. Otherwise, the nomenclatural disruptions caused by the necessary acceptance of the names with relatively detailed descriptions will be unavoidable, and requests for binding decisions will need to be repeated for many other problematic names. To avoid all these problems and to maintain the stability in current taxonomy and nomenclature to the largest extent possible, we here propose to suppress the work of Diels (l.c.).

It is worth noting that there are two other catalogues of Forrest's collections (Smith & al. in Notes Roy. Bot. Gard. Edinburgh 14: 75–393. 1924 & 17: 1–406. 1929–1930; prepared for the fifth and fourth expeditions, respectively). They are organized in the same format as that of Diels (l.c.), and both contain some names presenting the same problem as discussed in this proposal. However, the problematic cases are many fewer, with six and five being located, respectively. Meanwhile, they contain four and one currently widely accepted combination, respectively. For these two works, requesting binding decisions for the problematic cases would seem a more desirable solution, and it is done in parallel with requests by Wang & al. (in Taxon 69: 837–839. 2020).