INTRODUCTION AND APPENDIX. xvii 
and Malvacee of America and Europe are no less striking than is the comparative 
rarity in the former country of Cruciferze, Caryophyllee, Geraniacee, Carduacee, 
Campanulacee, Lobeliaceze, Primulaces, and Orchidex, and the prevalence of Vitacex, 
Anacardiacee, Crategi, Asclepiadeee, Polemoniacer, Nyctaginex, and Cyperacez. 
Turning now to the Floras of the Asiatic and American continents, it is difficult to 
say which is the most striking phenomenon, the wonderful identity of certain isolated 
genera and species of the eastern shores and islands of the Old World with those of 
the eastern side of the New World (and which has been so admirably worked out 
and explained by Asa Gray), or the total dissimilarity of the Asiatic and American 
temperate Floras in other respects. I may select the Japan group in illustration of 
both phenomena, because geographically it is perfectly well suited for a comparison 
with the Pacific-coast Flora of America, and because it is the head-quarters in Asia 
of the representative genera and species of the Eastern American Flora. The Japanese 
Flora contains about 200 species common to North America, but nearly three fourths 
of these are species found all round the globe in the north temperate regions; the 
remainder are chiefly the Eastern American genera and species alluded to above. 
Of the North-American Flora proper there is not a trace in Japan; there is not one 
of its multitude (nearly 150) of peculiar genera to be found in Japan of Cruciferae, 
Capparidee, Papaveracee, Rosaceze, Saxifragee, Onagracee, Composite, Polemo- 
niaceee, Hydrophyllaceee, Scrophularinee, Nyctagineee, Polygonez, and Liliacex, nor 
are there any endemic representatives of them. Further, the numerical proportions 
of the Japanese orders are European and Asiatic, not American. Leguminose, of 
which there are only 19 genera in California, is represented by 41 in Japan; though. 
the total number of phanerogamous genera is 879 in California and only 839 in Japan. 
Of Orchidee there are only 10 genera and 22 species in California against 34 genera 
and 67 species in Japan*, and the contrast might be carried much further by taking 
many other natural families. In short, the differences between the Palearctic and 
Nearctic botanical areas are so many and various that I have no hesitation in 
regarding them as two botanical kingdoms. 
Il. The tropical Kingdoms of the Old and New World.—<An analysis of the Floras 
of the Old and New World as a whole shows, as was to be anticipated, that the Old 
World Flora is by far the richest ; it contains probably 6000 known genera of Flowering 
Plants, and the New World nearly 4000, there being only about 1200 genera common 
to both. It is a singular fact that the ratios of Monocotyledons to Dicotyledons is the 
same for the endemic genera of the Old World (1°48), for the endemic genera of the 
New World (1:46), and for the genera common to both (1°47). How far this holds 
* The Californian genera of Orchids are, with one exception, European, and most of them Asiatic, which 
renders the absence of so many in Japan very anomalous. 
