THE FLORA OF MANILA. 203 
another, and others inadvertently. In other parts of the Archi- 
pelago additional species of American origin occur which are 
not now found in or near Manila, while in other neighboring 
countries of the Indo-Malayan region there are a certain number 
of other species, also of American origin, which have not as yet 
reached the Philippines. In the entire Indo-Malayan region it is 
probable that there are to-day, either in general cultivation or 
as weeds, more than 200 species that have originated in tropical 
America and which have found their way into the Eastern 
Hemisphere since the advent of the Europeans, that is, within 
the past 400 years. 
In the interchange of species between the Old World and the 
New, those originating in tropical America and now occurring 
in the Indo-Malayan region are apparently much more numerous 
than those of oriental origin which have been introduced into 
tropical America. This seems to apply not only to the ubiquitous 
weeds of cultivation, but also the economic plants, especially those 
that are cultivated for food. 
Without access to extensive and representative collections of 
tropical American plants, it is impossible properly to deal with 
the subject of introduced plants in the countries extending from 
Mexico southward to Brazil, either of oriental or other origin. 
That many species from the Indo-Malayan region have been 
introduced into tropical America is a fact, but it is impossible to 
form a clear conception of the number, and especially of their 
abundance, without some personal knowledge of the floras of 
the latter region. Species that are merely cultivated are as a 
general rule ignored by botanical collectors, and for this or for 
other reasons are frequently excluded from botanical works 
treating of restricted areas. From an examination of the liter- 
ature available here I have been able to compile a list of only 
about 80 species of Indo-Malayan origin that have purposely been 
introduced into tropical America, and which are for the most 
part only cultivated there, although naturally some have become 
established where favorable conditions exist. As to how general 
these species are in the great area included in tropical America, 
I have.no information, but many are doubtless of very local occur- 
rence. As to weeds of cultivation I have found records of only 
about twenty species that are to a greater or less degree distrib- 
uted in tropical America, and which have undoubtedly originated 
in the Old World, and are of inadvertent introduction into the 
New, 
It is apparent that by far the greater part of our ubiquitous 
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