II. ON A COLLECTION OF PLANTS FROM 



PENINSULAR SIAM. 



By H. N. Ridley, C.M.G., F.R.S. 



The plants dealt with in this paper were collected by 

 the Federated Malay States Museums during a general 

 biological expedition, extending from January to March 

 1919, to the Islands and West Coast of Peninsular Siam 

 between Lat. 7 and Lat. UN. 



Hitherto very little collecting has been done in this 

 area though Mr. C. Curtis collected at one time in Puket, 

 Trang and Pangnga while Renong has long been a favourite 

 centre for orchid collectors. North of this region lie the 

 Mergui Archipelago and Tenasserim, the floras of which 

 were extensively collected by Griffith and Heifer.^ 



The typical lowland Malayan flora, that of the dense 

 wet forests of the Malay Peninsula, disappears rapidly as we 

 reach the dryer regions of Kedah, Setul and Perlis, where 

 it is replaced largely by South Burmese and Siamese plants ; 

 as we go still further north Malayan plants become again 

 fewer but it is clear that many have contrived to push their 

 way through the dryer regions into the northern parts of 

 Peninsular Siam and into Tenasserim. 



Two instances in the present collection are 

 Pentaphragma begoniaefolia and Cyrtandra bicolor, both 

 of wmch find their furthest limit here. Well represented 

 in southern Malaya the species of these two genera become 

 more scanty the further north we go until they disappear 

 in this region. 



The coUection is remarkably strong in Acanthaceae 

 with one new genus, and a number of new species. 



Acanthaceae are comparatively rare in the southern 

 Malay Peninsula becoming more abundant in the dryer 

 northern region. The occurrence so far north of Thottea 

 (Aristolochiaceae) and of the common southern 

 Bromheadia palustris (Orchidaceae) in Takuapa, its most 

 northern limit, are important extensions of range. 



Among the most interesting novelties are the fine 

 Capparis Klossii ; Eloeocarpus tectonaefolius, only allied 

 to a Javanese species ; the stiff -leaved Canthium trachy- 

 style ; Vallaris macrantha, with unusually large leaves and 

 flowers for the genus ; the new genus of Acanthaceae, 

 Antheliacanthiis, remarkable for its small almost regular 

 corolla ; Xyris tuberosa, with its remarkable rhizome of 

 globose joints ; and Carex mapanifolia, with its dense 

 spikes and broad leaves, allied to C. Helferi of Tenasserim 

 and C. scaposa of China and Cochin-China. 



I Dr. A, Keith collected in Bangtaphan, South-western Siam (between 

 the latitudes of Renong and Mergui) in 1890-1, and his specimens form part 

 of the material on which are based Mr. Ridley's botanical papers in the 

 "Journal of the Straits Branch Royal Asiatic Society," No. 59, July 1911, 

 pp, 15-234 [C.B.K]. 



