IX, C,1 Merrill: Plants of Guam 33 
O. Ktz.,Urena lobata L., Commelina nudiflora L., Phaseolus ade- 
nanthus Mey. (P. truxillensis H. B. K.), Bidens pilosa L., Eclipta 
alba Hassk., Solanum nigrum L., and Oxalis corniculata L. 
On my basis of origins of these pantropic weeds we have to 
account for the presence of but very few “American” weeds in 
Polynesia before the region was visited by the botanists of 
Cook’s voyages. Many of the species enumerated by Seemann 
and by Guppy are either confined to the tropics of the Old 
World, or are of pantropic distribution originating in the Old 
World, and would be apt to be distributed through Polynesia by 
the Polynesians themselves. It is conceivable that some of the 
species were distributed from one hemisphere to the other by 
natural causes, but it is considered that a prehistoric pantropic 
distribution for most of the species is exceedingly improbable. 
In Guppy’s and Seemann’s lists we have to account for the 
presence in Polynesia, before the middle of the eighteenth cen- 
tury, of such species as Ageratum conyzoides, Waltheria amer- 
icana, Ipomoea bona-nox, Physalis angulata, and Teucrium in- 
flatum if I am correct in my deduction that these are of American 
origin. 
Cook’s voyages of discovery in the last half of the eigteenth 
century were by no means the first visits by Europeans to Poly- 
nesia. The seeds of such plants as those enumerated above, 
as well as many others, may very readily have been disseminated 
by some of the earlier Spanish, Dutch, English, and French 
explorers, such as Alvarez de Mendano (1567), Drake (1577), 
Cavendish (1586), Mendana de-Neyra (1595), Van Noort 
(1598), Quiros (1605), Spilbergen (1616), Schouten and Le 
Maire (1615), Hermite (1625), Dampier (1686), Cowley (1685), 
Clipperton (1691), Rogers (1710), Roggewein (1721), Anson 
(1742), Byron (1764), and Bougainville (1767), who came into 
the Pacific from the American side with from one to several 
ships each. The Acapulco-Manila galleons must also be taken 
into consideration in the introduction of American weeds into 
the islands of the Pacific, the sailings of which extend over a 
period of approximately three hundred years from the beginning 
of European colonial history in Polynesia and the Philippines, 
a period preéminently characterized by an interchange of 
economic species and weeds between the eastern and western 
hemispheres. ; : 
We know from Captain Cook’s own statements that he took 
with him into the Pacific live stock consisting of horses, cattle, 
sheep, goats, and domestic fowls for distribution to the Poly- 
122958——3 
