XXxvi INTRODUCTION. 
Mongolia. In the present comparatively early stage of an enumeration of Chinese 
plants * the data are not forthcoming to describe exactly where this subregion should 
be bounded, but it is warm temperate in climate, and characterized by having a very 
large woody element, with intimate Himalayan and Eastern North-American connec- 
tions. Rarity of annual plants is also strongly marked. Collections received since the 
publication of the parts of the ‘Index’ issued have very largely augmented the num- 
bers of genera and species, especially of the earlier orders, which were elaborated before 
even the first collection came to hand, Therefore data taken from it alone are im- 
perfect beyond even what is known of the flora. To give some idea of the large 
number of species concentrated in a small area, it may be mentioned that Dr. A. Henry 
has collected upwards of a thousand species of flowering plants within a short distance 
of Ichang, and at a very moderate estimate ten per cent. of them were previously 
unknown. 
A rough analysis of the Polypetale enumerated in the ‘Index’ gives a total, exclud- 
ing cultivated and doubtful ones, of 1514 species belonging to 476 genera and sixty- 
six (out of a total of eighty-five) natural orders. Fourteen of the genera and 626 (or 
41:3 per cent.) of the species are apparently endemic, but these figures do not represent 
the true proportions, because all the common plants of the coast districts are 
included, and it is very imperfect as far as regards the interior.’ The small number of 
species to a genus (about three), half the number found in the larger areas examined, 
has already been commented upon. The distribution of the non-endemic species in the 
above total, so far as it is known, is as follows :—140 extend to Japan only; 90 to India 
only; 27 to India and Japan only ; 273 others are restricted to Asia, inhabiting some 
other part or parts than Japan or India, or besides Japan and India; and the remaining 
397 (nearly a quarter of the non-endemic) are of wider range. 
Other remarkable features in the Chinese Flora are the great latitudinal range of some 
of the species, and the high northern localities of some subtropical types, such as 
Nelumbo, Euryale, and Cedrela. ‘The same phenomenon is exemplified in the animal 
kingdom. 
Returning to the New World, it will be seen that Wallace’s Rocky Mountains 
subregion embraces the North-Mexican province, as roughly defined in vol. iv. pp. 139 
and 306, and the country northward to about 55° Jat., and from about 97° long. west- 
ward to the coast range ; thus covering the whole prairie and treeless regions, the central 
mountain-range, and Lower California. The corresponding botanical subregion occu- 
pies a similar but rather more restricted area, and it is essentially a dry one, falling 
into several provinces, one of which, the North-Mexican, is approximately defined 
and characterized in the place cited. Dr. Asa Gray and Sir Joseph Hooker seem to 
have had some such division in view, though they do not go the length of actually 
* « Index Flor Sinensis,” Forbes and Hemsley in Journ. Linn. Soc., Bot. vol. xxiii. 
