24 
The Philippine Journal of Science 
1914 
of 193 of the 471 known genera; and of 36 of the 107 known 
families. That is, 36 families, 193 genera, and 314 species are 
represented in the Guam flora only by purposely or inadvertently 
introduced plants. In many other families and genera, which 
have some indigenous representatives, the percentage of intro- 
duced species is high and of indigenous ones is low. 
It is evident that Guam has ocupied a very important place in 
the dissemination of weeds of American origin to the islands of 
the Pacific, both in Micronesia and in Polynesia, during the 
second or galleon period. We know that in this period some 
scores of American economic plants and weeds were introduced 
into the Philippines from Mexico, 4 and we now know more defi- 
nitely just how many were then introduced into Guam. That 
many of them were thoroughly established there over one hun- 
dred twenty years ago is proved by the fact that some were 
then collected in Guam by Nee and by Haenke, and at a some- 
what later date by Lesson, Chamisso, and Gaudichaud. Most of 
the species of American origin were introduced into Guam dur- 
ing the period of the Manila-Acapulco galleons, or before the 
year 1815. It is interesting to note that many of these species 
are now dominant in Guam in suitable habitats ; that is, the open 
country, waste places, fallow fields, deserted clearings, along 
trails, etc. Then too, while most of the weeds of American 
origin are now found in all tropical countries, a considerable 
number are found outside of tropical America only in the Philip- 
pines, in the Philippines and Guam, or in Guam alone. I 
have elsewhere discussed this matter, so that it is unnecessary 
to enter into details here, but it is significant of the effect of 
ancient trade routes on the vegetation of a region, even when 
the communicating countries are separated by the breadth of 
the Pacific, when we find for the most part confined to Guam and 
the Philippines, or to one or the other of the above, such Amer- 
ican weeds as Malachra fasciata Jacq., Hyptis capitata Jacq., 
(now in Java), Hyptis spicigera Lam., Elephantopus mollis 
HBK., Elephantopus spicatus Aubl., (now in Hongkong), Ipo- 
moea triloba L., (now in Singapore, Java, and Mauritius), 
Blechum brownei Nees, (now in Formosa), Anredera scandens 
Moq., Ammannia coccinea Rottb., Rotala ramosior Koehne, Alter- 
nanthera frutescens R. Br., Portulaca pilosa Linn., Gliricidia 
sepium Steud., Schrankia quadrivalvis Merr., Parosela ( Dalea ) 
* Merrill, E. D. Notes on the Flora of Manila with Special Reference 
to the Introduced Element. Philip. Journ. Sci. 7 (1912) Bot. 197-202. 
