12 INTRODUCTION. 
А region similarly outlying and similarly destitute of distinctive features is the North- 
west Frontier or Indian Desert region. Here, again, there are three species. Two of 
these—D, lanceolaria and D, latifolia-—are very characteristic of India generally, though 
both cross the Gangetic plain to the Himalaya; the third is D. 55800, а species very 
charaeteristie of the sub-Himalayan forests from Assam to the Panjab and Beluchistan, 
but rarely, if ever, met with wild to the south of the Gangetic plain and Rajputana. 
As the desert region has thus two species that are characteristic of the Indian Peninsula 
as against one that is characteristically sub-Himalayan, we may treat the area as an 
annex of India Proper, though, just as Ceylon is a meeting place of Indian and Malayan 
influences, India Deserta is a meeting place of Indian and Himalayan influences. 
Existing political boundaries and ethnological considerations render it not inexpedient 
to divide South-Eastern Asia into five fairly equal botanical provinces: India; Indo-China ; 
China; Malaya; Papuasia, india may be further fairly naturally subdivided into four 
sub-areas; (1) Malabaria, including Ceylon, Malabar, and the Сопсап with the hinterlands 
of the two latter as far eastward as the influence of the south-west monsoon is directly 
felt; (2) Coromandelia; Coromandel, the Dekkan, Central India, or the whole Indian 
Peninsula to the east of Malabaria and south of the Gangetic plain; (3) India Deserta ; 
the area of scanty rainfall in Scinde, Rajputana, the Panjab, and along the trans-Indus 
frontier; (4) the Himalayan ranges, from the Indus to the Brahmakand, through which 
the waters of the Sanpo reach the Brahmaputra. Indo-China seems to lend itself 
to further subdivision into the following subareas: (1) Assam-Arracan; a block of hill- 
ranges lying between the Brahmaputra and the Irrawaday rivers, and extending from 
the Mishmi-Kachin countries, which are of Himalayan character and which border on 
Tibet and China, as far as the Andaman islands, which are a southward prolongation of 
the Yomah of Arracan and havea mixed Burma-Malay vegetation; (2) Shan; another 
rezion of hills and plateaux lying east of the Irrawaday, hounded on the west by the 
Mekong as far south as 20° М, lat, afterwards by the Meinam; this subarea 
includes to the south 'l'enasserim, where, again, there is a marked Malayan element in 
the vegetation; (3) Siam-Anam; a region of plains and lower hills extending southward 
from 20° N. lat. and east of 100° E. long. including Siam, Laos, Cochin-China 
generally, In the extreme north-east of Indo-China lies the province of Tongking, too small 
to be considered a subarea apart, yet, so far аз the genus Dalbergia is concerned, calling for 
special treatment. Hitherto only four Dalsergias have been definitely recorded from 
Tongking—none of them endemic; if we except 2. torta, which occurs on nearly every coast 
throughout South-Eastern Asia, and is not therefore characteristic of Indo-China in particular, 
none of the four occur either in the Anam-Siam or in the Skan subareas, One of the 
Tongking species—D. rimosa—is characteristic of the Himalayan area, where it extends 
from Sikkim to Upper Assam; of the northern portion of Western Indo-China, where it 
extends from Sylhet and Cachar to Kachin; and of South-Western China (Yunnan), 
The other two species—D, Bulansae and D. tonkinensis—extend to Tongking from South- 
Eastern China, There is a fifth species, the identity of which is doubtful, in the same 
area. This is D. pinnata (Derris pinnata Lour.) usually identified with D. tamarindifolia, 
which, if Loureiro’s description be exact, cannot well be the case. The diagnosis given by 
Loureiro agrees best with the description of D. Millettii: should the two prove to be 
the same, then Tongkiug bas three species that extend from South-Eastern China. 
Tongking has been only inadequately explored botanically, and the absence of forms 
peculiar to the province or common to Tongking and Central Inlo-China, or to Tongking 
