1 108 
Ward. — Some Plant Formations from the 
occurs, not in the easternmost valley, which is already shut out of a great 
part of its normal rainfall, but in the most westerly— the valley of the 
Salween ; nothing indeed could be more striking than the abrupt change 
from semi-tropical jungles in the southern rainy part of the valley, to semi- 
desert further north, a change rendered all the more striking by a correlated 
change in the people, from the tribesmen of the jungles to the Tibetans of 
Tsa-riing in the north. 
Granite occurs frequently in these valleys, and can be recognized from 
a distance by the clumps of Prickly Pear ( Opuntia vulgaris) which grow 
amongst the ‘ tors ’ and boulders of the weathered rock ; it apparently 
grows nowhere else but on granite rocks, and, conversely, wherever granite 
occurs there also will be found the Prickly Pear. Its interest lies in the 
fact that Opuntia vulgaris is a native of Mexico or California, and it is worth 
while inquiring how it found its way into Western China. I have traced 
it from Kansu through SsU-chuan to South-East Tibet and Southern 
Yun-nan, cultivated of course for the sake of its fruit, and such a wide, 
if discontinuous, distribution at that distance from its original home is 
curious. 
It is not of course the only plant which has wandered far from its home 
under circumstances hitherto unexplained, or merely conjectured ; we need 
only instance the maize, also said to be a native of Mexico, now cultivated 
throughout the world. But a cereal of such general utility as maize, in 
common with rice and other staple grains, was probably distributed over 
the globe from the very earliest times, whereas such is not likely to be the 
case with Opuntia , which after all is of no very great importance as a source 
of food. 
Two suggestions present themselves, — the first that it was brought 
across the Pacific by the Chinese themselves, the second that it was intro- 
duced from Europe after it had been brought into the Mediterranean region 
from across the Atlantic ; a third alternative, that it was quite recently 
introduced by the Jesuit missionaries who came from America to China 
about the time of the fall of the Spanish Empire, is hardly tenable in view 
of its present wide distribution in Western China. 
There can be little doubt that the Chinese visited California long before 
Columbus or possibly even the Norsemen discovered America, being carried 
across the Pacific accidentally by the Kuro Shwio, and voyaging across 
it when the intrepid Chinese mariners sailed those seas to the Indies, to 
Japan, perhaps even to Australia. It is equally well established that there 
was considerable intercommunication between Europe and Asia, particularly 
between Greece, India, and China, in very ancient times ; and if during this 
intercourse ideas on art and religion were exchanged, it is highly probable 
that other things were also, more especially useful plants and the ordinary 
commodities of trade. 
