species in Thailand and Indochina fall into three
distinct, though parapatric, geographical units (Boyce 1996). Two
of the 14 species, P. chinensis
(Raf.) Merr. and P.
L., have a Indohimalayan distribution, occurring
more-or-less continuously from the eastern Himalaya (as far west
as Nepal) to southern China (east to Hong Kong and north to Hubei)
and south to peninsular Thailand. However, the distribution of P.
occurs throughout Indomalesia east to the Philippines
and extends south and west to Madagascar.
Seven species (P. dzui
Buchet ex. P.C.
Boyce, P. grandis
Buchet ex. P.C.
Boyce & D.V. Nguyen, P. kerrii
Buchet ex P.C. Boyce, P. pilulifer
Buchet ex. P.C. Boyce, P. repens
(Lour.) Druce and P. touranensis
Gagnep.) are restricted
to Vietnam, Lao P.D.R., southern China and possibly Cambodia (P.
). Based on inflorescence morphology, relationships
of outside the region appear to be with Javan P. junghuhnii de Vriese
, P. kerrii
], the Malesian complex of
P. barberianus [P. touranensis
] and Sulawesi/Philippines
P. cylindricus Presl [ P. repens
and maybe P. dzui
Four species (P. kingii
Scort. ex Hook.f. and P. curtisii
Hook.f.) occur widely in Peninsular Malaysia (P.
also reach Sumatera) and their range in
the review area is restricted to the southernmost provinces of peninsular
Thailand where they are confined to limestone (P.
, P. macrocephalus
and granite (P. kingii
One species, P. lancifolius
Hook.f., has a curious disjunct distribution with sites in Peninsular
Malaysia and southern central Vietnam (where it has been called
hitherto P. penicilliger Gagnep.). Relationships with other species
outside the area are not clear although an as yet undescribed species
similar to P. lancifolius
is found in Borneo.