l8 TlMEHRI. 
races. In the temperate zone the weeds of colder 
climates flourish in the open field, but when they have 
become naturalized in the tropics, they acquire the 
habit of sociability, flourishing only near houses and in 
gardens. While the garden and field pests of temperate 
climates are spreading all over the world and making 
their appearance within the tropics, the large family of 
East and West Indian weeds are making their way into 
Southern Europe. In the great struggle for existence 
these plants have become strong and vigorous, armed 
with stiff spines or hairs, built up with wiry and fibrous 
stems, and flavoured with disagreeable tastes and smells. 
Like a legion of invaders they are marching over the 
world, gradually driving the native plants farther and 
farther, until ultimately as man advances, the Botanist 
will hardly be able to find a specimen of the characteristic 
flora. The most noticeable instances of weed aggression 
will be found on small islands. The native vegetation 
has almost disappeared from Barbados and Madeira, 
while in St. Helena where certain species were peculiar 
to the island, some of them will soon be found only as 
specimens in our great national herbaria. A tree in the 
last island has lately been figured in the " Gardener's 
Chronicle" as the " last of the race." 
In this colony man has done very little to modify 
nature, but the work is progressing slowly, and as the 
swamps are drained the native plants are being 
gradually driven farther and farther, to make room for 
about a hundred species of foreign plants which are 
generally unsightly and disagreeable. The line of cul- 
tivation on the coast and up the rivers is coincident with 
a distinct flora, which could not have existed in the 
