200 MERRILL. 
The majority of the above species are found only in cultivation, 
but some, such as Leucaena glauca Benth., Mimosa pudica L., 
Argemone mexicaiia L., Lantana camara L., Cosmos caiidatus 
HBK., Acacia farnesiana Willd., Gliricidia septum Steud., Psid- 
ium guajava L., Jatropha curcas L., Pithecolobium dulce Benth., 
Ipomoea nil Roth, and Pachyrrhizus erosus Urb., are so thor- 
oughly naturalized and so common and widely distributed in the 
+ 
Philippines that the casual observer would consider them to be 
indigenous species. 
In addition to the species above enumerated that were orig- 
inally purposely introduced and which have become thoroughly 
naturalized, we must now consider a very large number of trop- 
ical weeds that have originated in America, which were inad- 
vertently introduced here and which have now extended their 
range, certainly through the agency of man, to most tropical 
countries. Among these American aliens may be mentioned the 
following: Paspalum conjiigatum Berg,, Cenchrus echinatus L., 
ChloTis barhata Sw., Peperomia pellucida HBK., Pilea micro- 
phylla Leibm., Celosia argentea L. (possibly introduced for or- 
namental purposes), Alternanthera fii^tescens R. Br., Cassia tora 
L., C occidentalis L., C. hirsiita L., Zoi^nia diphylla Pers., Des- 
modium scorpiurus Desv., D, procumbens Hitchc, Par^osela glan- 
dulosa Merr., Crotalaria incana L., Phaseolus semierectus L., 
Euphorbia prostrata Ait., Malvastrum coromandelinum Garcke, 
Malachra capitata L., M. fasciata Jacq., Triumfetta bartramia 
L., {T. rhomboidea Jacq.), T, semitriloba Jacq., Waltheria ameri- 
cana L., Passiflora foetida L., Rotala ramsoir Koehne, Jussiaea 
linifolia Vahl, Asclepias curassavica L., Ipomoea triloba L., Lip- 
pia nodiflora Rich., Stachytarpheta jamaicensis Vahl, Hyptis 
suaveolens Poir., H. brevipes Poir., H, capitata Jacq., H. spicigera 
Lam., Physalis angulata L., P. minima L., Scoparia dulcis L., 
Elytraria tridentata Vahl, Blechum broiunei Juss., Ageratum 
conyzoides L., Elephantopus scaber L., E. mollis HBK., E. spi- 
catus Aubl., and Synedrella nodiflora Gaertn. 
Nearly all the species in this last list of American weeds are 
very common and widely distributed in the Philippines. Most of 
them are confined to the settled areas, and are so thoroughly 
naturalized that they might well be considered indigenous species 
if nothing were known of their origin. Many are individually 
numerous, that is more dominant, than are native species, or 
those that have been introduced from the tropics of the Orient. 
While most of these American weeds are now found in most 
tropical countries in the East having proper cUmatic conditions 
