xvi FLORA OF THE VITIAN ISLANDS. 
naturalized in such parts of Europe as are suitable to them in climate and soil; the reason 
seeming to be that weeds do not spread except in countries or areas to them altogether 
virgin, which, for geological reasons, Australia and the southern parts of North America are 
not held to be with regard to Europe, Australian vegetation having covered Europe during 
the Eocene period, and North-American during the Lignite. 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 may make an attempt to deal with it as far as Viti 
is concerned. 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. Polynesia 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 plants altogether 
virgin ground. In the following list of Vitian weeds those marked with an asterisk (*) have 
also been found in America, but I have excluded all swamp and water plants, as well as 
herbs growing close to the seaside, just above high-water mark, such as Zpomea Pes-capre, 
Triumfetta procumbens, etc., which cannot properly be regarded as weeds in my definition 
of the term, because they indi one of the most essential characteristics, viz. to spread on 
land cultivated or otherwise disturbed by the agency of man :— 
*Cardamine sarmentosa, Forst. 
_*Portulaca oleracea, Linn. 
Portulaca quadrifida, Zinn. 
*Talinum patens, Willd. 
f Sida microphylla, Cav. 
|*S. rhombifolia, Linn. 
1*8. linifolia, Cav. 
*Urena lobata, Linn. 
*Waltheria Americana, Linn. 
*Oxalis corniculata, Linn. 
*Cardiospermum Halicacabum, H. B. K. 
*Crotalaria quinquefolia, Zinn. © “ 
*Indigofera Anil, Linn. 
*Desmodium polycarpum, De Cand. 
Uraria lagopodioides, De Cand. 
*Phaseolus Truxillensis, H. B. K. 
*Lablab vulgaris, Sav. 
* Abrus precatorius, Linn. 
* Cassia levigata, Willd. 
C. Sophora, Linn. 
*C, obtusifolia, Linn. 
*C. glauca, Lam. 
*C. occidentalis, Linn. 
*Mimosa pudica, Linn. 
*Hydrocotyle Asiatica, Linn. 
Hedyotis Cratwogonum, Spr. 
*Oldenlandia tenuifolia, Forst. 
= O. paniculata, Linn. 
*Geophila reniformis, Cham. et Schlecht. 
*Ageratum conyzoides, Linn. 
Adenostemma viscosum, Forst. 
*Erigeron albidum, 4. Gray. 
