IX, C, 1 
Merrill: Plants of Guam 
27 
definitely natives of the eastern hemisphere, Adenostemma vis- 
cosum and Chenopodium album, while six are equally definitely 
of American origin, Sida glomerata, Ammannia coccinea, Oes- 
trum diumum, Physalis lanceifolia, Hyptis pectinata, and Mi- 
tracarpum hirtum, and with the possible exception of Oestrum 
diumum were all accidentally introduced into Guam. 
The original vegetation of the Polynesian islands is mainly of 
Malayan origin, and like aboriginal man, the present species of 
plants, or their ancestors, entered the Archipelago from the west. 
Most of the original food plants of the Polynesian people were 
carried with them from island to island in their migrations, or 
in their later intercommunication between islands and groups 
of islands, and with very few exceptions are manifestly of 
Asiatic or Malayan origin. The coconut is a striking exception, 
for this is probably of American origin. 
Seemann* has briefly considered the weed flora of Polynesia, 
but I do not agree with him in his conclusions. He states : 
“Polynesia, situated as it is between three great continents, presents a 
most interesting problem with regard to its weeds, which, however, cannot 
be satisfactorily solved until the whole flora shall have been properly 
worked out; but we make an attempt to deal with it so far as Viti is con- 
cerned. There we have 64 species, which may be regarded as troublesome 
weeds. Some of these are diffused throughout the tropics; but the bulk of 
them (48) are common to America, only 16 being strictly confined to the 
Old World, principally Asia. It may be argued that several of those found 
in America are also common to Asia, or that Asia is their true native 
country; but even admitting this reduction, it must be conceded that the 
bulk of the weeds of Viti is of American origin, or at all events, is now 
found in America. This is the more singular as the majority of the 
species of these Islands, as far as they are not endemic, is Asiatic. Poly- 
nesia seems to have acted as a bridge by means of which the weeds of the 
Old World crossed over to the new, and those of the New World to the Old; 
and the fact that American weeds show a greater disposition than Asiatic 
to spread in Viti must be held to prove, if my theory be sound, that Viti 
is to American weeds altogether virgin ground. 
Seemann confined his list of weeds strictly to those plants 
that are characterized by their ability to spread on land cultivated 
or otherwise disturbed by man, and definitely excluded all strand 
plants, aquatics, and marsh plants. His list of weeds, then, is 
not directly comparable to my list of pantropic species. Of 
his list of 64 species, 48 are credited by him as occurring in 
America, but this must now be raised to at least 50. In analyz- 
ing his list of Vitian weeds, however, I find not more than 12 
that I consider to be definitely of American origin, about 32 
s Flora Vitiensis (1865) XVI. 
