American Orchid Society Bulletin - 54(1): 61-65 (Jan 1985)
Phragmipaphiums — Are They Possible?
Donald Wimber and John Hanes

IT IS NOT SURPRISING that matings between genera as similar as Paphiopedilum and Phragmipedium have been attempted many times. A perusal of the early years of The Orchid Review identifies several cases. Apparently, seed and seedlings were frequently produced in these crosses but most plants proved to be recalcitrant bloomers. We are indebted to Professor Charles Hurst for information about the flowering or non-flowering of these “hybrids.” Hurst was acutely interested in wide crosse among the orchids and wrote in the British journal Nature in 1898, “More than twelve distinct crosses have been raised, but so far all resolutely refuse to flower … and many of them are not large, vigorous plants, long past the usual flowering age. … Many of the remaining plants … are distinctly intermediate in their foliage and habit of growth, and clearly bear the stamp of their recorded parentage.” In a rather extensive paper the same year entitled “Notes on Some Curiosities of Orchid Breeding,” Hurst (1898) enumerates some 13 Phragmipedium x Paphiopedilum hybrids, only one of which had flowered and it closely resembled the pod parent. In a republication of this paper (1925), we find a footnote added in 1914 that gives more information about individuals from three crosses that he raised: “Only five survived to flower and all flowered true to the mother species with no trace of the pollen parent'.” So we are left to conclude that parthenogenesis (asexual reproduction) or accidental selfing or both may have played a role in producing these intergeneric “hybrids.”

In 1912, Selenocypripedium Malhouitri (Paph. Harrisianum X Phrag. schlimii) was registered by a Mr. Boullet. In those days, Phragmipedium and Selenipedium were often placed in the same genus and paphiopedilums were considered cypripediums by many. The description of the flower in The Orchid Review (Anonymous, 1913) was cryptic (there was no picture) but we are told that the lip was smaller than either parent.

Wilson (1961) registered and reported with a picture Selenocypripedium Confusion (Phrag. Grande X Paph. J. H. Walker). The actual hybridization, however, had been at the commercial firm of Mansell and Hatcher. Wilson saw little evidence of intergeneric hybridity because the flower closely resembled the Paphiopedilum parent. It seems likely that this was just another “false hybrid” similar to those that Hurst reported nearly 50 years before.

Several extensive cytological studies have been done with Paphiopedilum species by Mehlquist (1947), Duncan (1959), Karasawa (1979), and others. The chromosomes of this genus are uncommonly large and easily studied. Recently, the chromosomes of Phragmipedium have been scrutinized by Karasawa (1980), Atwood (1981), and Wimber (1983). It is clear that chromosome size in this genus is substantially smaller than that in Paphiopedilum. Chromosome numbers, too, although varying in both genera, tend to fall into different groups between Phragmipedium and Paphiopedilum.

In any hybrid between the two genera, one might expect to see both Paphiopedilum and Phragmipedium chromosomes within dividing cells and the chromosome shape and size should be preserved in the hybrid. Thus, it should be relatively easy to detect a true mating between the two genera by examining the chromosomes in the presumed hybrid. One of the authors of this paper (J.H.) has attempted dozens of these Paphiopedilum x Phragmipedium matings, and viable seeds were produced in only one instance.

A May 1970 cross of Paph. stonei with pollen from Phrag. Albopurpureum (Phrag. schlimii x Phrag. Dominianum) produced seeds that germinated. Several seedlings grew and many were sold. One was kept and subsequently bloomed on October 25, 1982 (Fig. 1). The flower clearly was not similar to the seed parent, Paph. stonei (Fig. 2). It was shown before the orchid judges at the American Orchid Society Pacific South Subregional Judging Center and most thought that it did seem to carry a substantial number of both the Paphiopedilum and Pragmipedium features (Fig. 3).

In the spring of 1983, the authors met to discuss this unique plant. We believed that here, at last, was an opportunity to demonstrate unequivocally that this particular intergeneric hybridization is possible. We collected root tips from all three plants, the two parents and the putative hybrid, now named Phragmipaphium Hanes' Magic 'Bion'. We anticipated that there would be a mixture of Paphiopedilum and Phragmipedium chromosomes easily distinguishable from one another by size and number that would give cytological proof of this intergeneric mating.

We found the following results: Paph. stonei, had, as it should, 26 large chromosomes (Fig. 4A) while Phrag. Albopurpureum had 35 smaller chromosomes (Fig. 48). The "hybrid" should have had 13 Paphiopedilum chromosomes and about 17 or 18 chromosomes from the Phragmipedium parent for a total of about 30. Phragmipaphium Hanes' Magic 'Bion', however, had only 26 chromosomes which closely resembled those of Paph. stonei (Fig. 4C) in size. This result clearly did not support an intergeneric origin. Furthermore, if Phragmipaphium Hanes' Magic was a result of parthenogenesis or accidental selfing, the flower should have closely resembled Paph.stonei.

Ordinarily, traditional cytogenetic rules would force us to conclude that it was probably an accidental hybrid between Paph stonei and conclude that it was probably an accidental hybrid between Paph. stonei and another Paphiopedilum also having 26 chromosomes. In other words, no Phragmipedium chromosomes, no intergeneric hybrid. Recently, however, reports of "counterfeit hybrids" have surfaced in other plants (De Wet, Newell and Brink, 1984). These are cases of wide hybrids where the maternal chromosome number has been preserved yet the offspring are clearly hybrid, i.e. hybrid in the sense that they show numerous features that could only have been obtained from the paternal parent. The usual explanation for these odd results is that the pollen tube enters the egg sac as in fertilization but true sexual fusion of the egg and sperm does not occur. Yet somehow bits and pieces of the paternal chromosomes become integrated into the maternal chromosome sets. The "counterfeit hybrids" have not been studied in enough detail to understand completely the mechanism for — and the extent of — their hybridity. We may be dealing with one of these counterfeit hybrids in the case of the Phragmipaphium a plant that has the 26 Paphiopedilum chromosomes yet has integrated some of the Phragmipedium genes into those chromosomes. Did Phragmipaphium Hanes' Magic have this origin? Did Phrag. Albopurpureum contribute hereditary material to the genetic makeup of the hybrid despite the negative evidence from its chromosomes? The judges at the Pacific South Subregional Judging Center were convinced that it had some Phragmipedium qualities.

If it does carry some hereditary units from Phragmipedium, they have not been passed on to the offspring in the usual way by the full sexual fusion of the egg and sperm. Phragmipaphium Hanes' Magic certainly deserves further study.

Despite the failure to confirm this intergeneric hybrid, a true sexual mating of Paphiopedilum and Phragmipedium might still be possible. After all, intergeneric hybrids between distantly related genera have been produced many times in orchids. Note the genuine hybrid between Ansellia gigantea (an African species) and Cymbidium canaliculatum (Australian) (Wimber and Kenney-Norberg, 1984) or the presumed Galeansellia Gondwanaland (Galeandra baueri from Central America x Ansellia gigantea