195 
WEEDS AND THEIR CHARACTERISTICS. 
J3y Berthold Seemann, Ph.D., F.L.S. 
So great are the changes constantly going on in the nature and 
aspect of the vegetation of the inhabited globe, that it is almost as 
difficult to conjure up by pen or pencil the flora of a country as it was 
a few centuries ago, as it would be that of any former geological 
rr 
period. By not taking these changes into account, those who endeavour 
to give us vivid pictures of the past, — historians, historical painters 
and romance writers,— often fall into the error of using, as a background 
for ancient historical events, the country in which they happened in its 
modern aspect, an anachronism as painful to a botanist as a wron 
note is to a musical ear. In a well-known print, representing Joseph 
sold by his brethren, the artist has carefully represented the Date-Palm 
and other features of the desert, but he has committed the blunder of 
introducing the American Cactus, which did not reach Syria till 
several thousand years after Joseph's death. Some time ago, I saw a 
play founded upon an incident of early Roman history. The stage ac- 
cessories had been executed with pre-Rafaelitic accuracy. There was 
the Roman landscape in all its beauty ; the melancholy Cypress, and the 
Stone Pine of Italy, the outline of which Pliny so happily compares 
with the smoke of Vesuvius as it hovered over the crater 1800 years 
go, and still hover3 in our year of grace ; but there was also, unfortu- 
nately, the American Aloe {Agave), which at present forms such a pro- 
minent feature of many a South European landscape, but was confined 
to the New World before the days of Columbus. 
Amongst plants a fierce though silent struggle for the possession of 
the soil is constantly going on. Even when no foreign elements are 
introduced into the flora of a country, it is ever at work ; but it be- 
comes much more fierce when species from abroad appear on the field, 
°r> at all events, from our beim>- able to recognize at a glance the op- 
posing elements, we are in a better position to watch the struggle 
antl its issue. A prominent example of such a battle-field, if so 
martial a term be admissible, is the island of St. Helena, where the 
native vegetation is almost entirely superseded by a foreign one, sonic 
of the singular indigenous tree- Cou/posil* and others now existing in 
0r 'ly one or two old specimens. In some parts of the Cape of Good 
B 
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1Io pe an equally great change is noted, and many species are in danger 
