By Will Tjaden

In No.70 May 1994, I showed how Epiphyllum truncatum '‘Ruckerianum’ superseded its synonym E. truncatum ‘Ruckeri’ from 1852 onwards. The underlying reason for the change was the practice by botanists in creating Latin names for new plant discoveries. If the necessary specific or varietal epithet was intended to record the discoverer or a botanist primarily concerned with describing the plant, the epithet would simply be his surname in the Latin genitive. Thus A.H. Haworth named Epiphyllum hookeri after the botanist Sir William Hooker who had first recorded it, although by mistake as Cactus phyllanthus. In English, Haworth had called the plant Hooker‘s epiphyllum. If, however, the epithet was intended to honour someone, that was done by adding '-ianus’ to the surname or 'ianum’ or 'iana’ according to the Latin gender of the genus. Thus George Gardner who discovered Schlumbergera russelliana in 1837, named it as Cereus russellianus in honour of his patron John Russell, 6th Duke of Bedford. The Duke had no claim to be thus recognised, but presumably did not object. Hooker, however, published the name as Epiphyllum russellianum.

From this it is clear that when William Rollisson wished to honour his important customer Sigismund Rucker with the epithet of a new variety of Epiphyllum truncatum he, Rollisson, had imported from Brazil, he should not have made it ‘Ruckeri’. This was the epithet Rollisson's nursery gave according to Paxton's Magazine of Botany in March 1845. Between then and 1852 Rollisson had substituted

'Ruckerianum’. I was wrong in saying that Paxton had correctly spelt it as 'Ruckeri' in paragraph 14 of my 1964 article in Gardeners Chronicle, but right in saying that the two names necessarily referred to the same variety. There is no evidence that the epithets were ever applied to different varieties. I wrote 'Ruckerianum' not 'E. Ruckerianum' in 1964 as a different name for the same variety Ruckeri'. E(piphylllurm) ruckerianum means a species. It was first published by Lemaire in 1861, nine years after Buckley's. E. truncatum var. ruckerianum, the stated pollen parent of his hybrids. On what I wrote in 1964 therefore it is not possible to infer "that the plant we know as S. x buckleyi was in fact, a hybrid between an intermediate and S. russelliana, and that S. truncata (sensu stricto) was not the pollen parent." (Christmas Cacti, p.40, third paragraph).

I agree with the statement in the second paragraph on page 40 that E. truncaturn var. ruckeri considered as an import from Brazil does not explain how one of Buckley’s hybrids might have arrived in Belgium under the name of E. ruckerianum in the 1850's (actually, arrived in France where Schlumberger, the authority for it, lived.) There is, however, no "strong presumption that E. ruckerianum (a species) was an import from Brazil", only that it was a variety of E. truncata. The list of cultivars given by Buckley in 1868 was under the heading Epiphyllum truncatum and its varieties. "Ruckerianum, purplish red tinged with violet" was included as one of them. Hence "ruckerianum was not marked as a hybrid" in the list.

The explanation in paragraphs 15 and 16 of my 1964 article still stands, that Continental nurserymen could have used the pollen parent’s name for Buckley’s hybrids instead of the seed parent E. russellianum used by Rollisson ‘s nursery. I wrote that "Some of them apparently omitted the cultivar names ‘Superbum’ and 'Rubrum’ (and ‘Snowii') thereby causing confusion between Buckley’s hybrids and the truncatum parent ‘Ruckerianum'. Certainly, the pollen parent name in full was so cumbersome as to invite misleading abbreviation. From E. truncatum var. ruckerianum 'Superbum' ('Rubrum' or 'Snowii') Lemaire was given only 'Ruckerianum'. The name was not always-wrongly quoted. In La Belgique Horticole 1868 p.62 a report on Paris flower markets said that "Epiphyllum Ruckerianum Hortul, var. rubrum et superbum, Ep. truncatum, Haw. var. spectabilis Cels,; et var. auranticum Hort.etc. abound still at present in the markets and florists of Paris".

There is a relevant statement in line 12 of page 18 of Christmas Cacti giving E. ruckerianum as the pollen parent, which needs amendment to E. truncatum var. ruckerianum.

Turning again to the third paragraph on page 40 of Christmas Cacti, it raises another possibility "that the female parent (of Buckley’s hybrids) was an intermediate rather than the true S. russelliana, particularly in view of Paxton’s (1843) illustration...." This illustration, reproduced as Plate 9, and Paxton's description, given on page 57 under ‘C’, support this. The ovary in Plate 9, however, is typical of all known collections of the species, and the stem-sections with bristles at the areoles are similar to those in Plate 7 reproducing the original drawing in Botanical Magazine Plate 3717. The sketches, but not the colouring, are similar in the two, although neither are like the two photographs in Plate 1.

What, however, is ‘intermediate’ and what is its difference from ‘hybrid’? Gardner said (Travels in Brazil, 1846 p.70) that he collected a great plenty of Cereus (Schlumbergera) russellianus and that it was a nearly allied species (to S. truncata), representing each other in different regions of the same mountain. ‘Great plenty’ would have given an opportunity for small differences (? intermediates) to be in his collection. He described the two as nearly allied species representing each other in different regions of the same mountain. S. truncata was always confined to dense virgin forests below 4500 ft. (1385m) but from there to the summit only S. russelliana was found, enjoying a more open and cooler region.

The difference in vegetation between lower and higher regions in each of the Organ Mountains would not be at exactly the same height above sea level, giving ample scope in the past for intermediate forms comprising features of either species to develop above and below Gardner’s 4,500 ft. The existence of intermediate forms, however, is justification for recognising only one species, Schlumbergera truncata var. truncata because it was found first, and Schlumbergera truncata var. russelliana. The great advantage for the hobbyist is that there is then no need for Schlurnbergera x buckleyi I apologise sincerely for its creation.