vi PREFACE 
early in February, 1900. The next two years were devoted by 
him to collecting in the mountains of western Hupeh. From 
this journey Wilson returned to England in April, 1902, and 
went to China again in January of the following year with a 
special commission to collect Meconopsis integrifolia, found only 
in the alpine regions of the Thibetan border, which he now 
explored for the first time. During these two journeys Wilson 
sent to England the seeds of a large number of plants and many 
lily bulbs, and made a considerable herbarium. His work, how- 
ever, in western China, was not completed. Under instructions 
from Mr. Veitch, Wilson had paid attention only to plants of 
supposed hortieultural value, and had neglected conifers and 
many other important plants almost entirely, no one then sus- 
pecting that on the slopes of the mountains which rise from the 
plains of China to the Thibetan plateau is probably the greatest 
aggregation of conifers in the world. 
It seemed desirable, therefore, that the work which Wilson 
had so well begun should be completed, and the Arboretum 
was fortunate in securing his services for another Chinese ex- 
ploring expedition. He left Boston on this journey on December 
31, 1906, and returned in May, 1909. This journey was very 
successful. He sent back seeds, often in large quantities, of 
more than 1000 species of trees and shrubs, many lily bulbs, 
the cuttings of willows and poplars, the roots of a few other 
trees and shrubs, an herbarium of about 50,000 sheets, and a 
collection of 720 photographs. In the autumn of 1908, when he 
was among the forests of conifers, these trees were not bearing 
cones. It was important that these trees should be introduced 
into the Arboretum, and in April, 1910, Wilson, for the fourth 
time, went to China for the purpose of carrying out this plan, 
returning a year later with large and valuable collections. 
In the Plantae Wilsonianae is found an account of the speci- 
mens collected by Wilson in these two journeys, with descriptions 
of new species and varieties, and the enumeration of several im- 
portant groups as they are represented in China. It is impos- 
sible yet to form an accurate opinion of the number of new 
