| Abstract: | Cypripedium subtropicum S. C. Chen et K. Y. Lang is a phytogeographycally significant new species with its habit, inflorescence and column very similar to
those of Selenipedilum of tropical America. It is found in Mêdog of southeastern Xizang, China. Its slender leafy stem bears at the summit a many-flowered raceme, amounting to 1.5 m in height. Although its ovary is unilocular—this is the reason why
we place it in Cypripedium, the column characters resemble those of Selenipedilum. For
example, the staminode is rather small and its long stalk is very similar in texture and
color to the filament of the fertile stamens. Obviously, it is a primitive new species related to Selenipedilum based on the similarities mentioned above.
In the subfamily Cypripedioideae, as generally recognized, Selenipedilum is the
most primitive genus, from which or whose allies Cypripedium is derived. Of phytogeographical significance is the fact that Selenipedilum occurs in Central America and
northern South America, while a cypripedium akin to it is discontinuously distributed
in subtropical Asia. This suggests that Selenipedilum or Selenipedilum-like form be
once continually distributed in North America and eastern Asia when the climate there
was warmer, as it is in the subtropics today. The floristic relationship between Central
America and subtropical Asia appears to be closer than expected, as shown by the distribution patterns of Tropidia, Erythrodes, etc. Based on the occurrence of all six sections and particularly the most primitive form in eastern Asia, Cypripedium seems to
be of Asian, rather than Central American, origin. Selenipedilum possesses some very
primitive characters, such as trilocular ovary, vanilla-scented fruit, seed with sclerotic
testa, simple column and more or less suffrutescent habit. The latter is considered by
Dahlgren & Clifford (1982) to be one of ancestral characters of monocotyledons, which
is now very rare not only in Orchidaceae but also in all monocotyledons. It is indeed
necessary to make further investigations on Selenipedilum and also the new species pub-lished here, as well as a detailed comparison between them. |
