ie 
33 
creatures, the answer might not unfrequently be given—to preserve 
the balance of life. 
In the balance of plant life, two very conspicuous agents played a 
part, viz., climate and soil. The former influence was possibly very 
slow ; the latter acted more rapidly in checking the multiplication of 
individuals, while to these a third might be added, the smothering of 
seedlings by other and more vigorous plants. A curious illustration of 
this last was seen in the common maple, thousands of seedlings of 
which sprang up every year near the parent tree, and were killed by 
the smothering influence of the summer grasses. / 
Man for the purposes of cultivation disturbed the soil, either at 
home or in the colonies, and the result was, the spread of certain 
plants at the expense of the native plants. A curious fact had been 
observed by many—the greater abundance of annuals in cultivated, as 
compared with uncultivated countries, indirectly pointing to the fact 
that disturbed soil seemed necessary to their existence. Some had 
even gone so far as to assert that were the land in any populated 
country to be depopulated, the common wild “annuals” would become 
either very rare or extinct. 
All must have noticed that when ground was disturbed, or a 
railway embankment made, plants such as the groundsell, shepherd’s 
purse, poppies, speedwells, oa annua, and other annuals, make their 
appearance the first year, while sometimes the ground was covered 
with an Zguzsetum ; the second year but few of these annuals were to 
be seen, their place being mainly occupied by biennials, such as 
__ coltsfoot, dandelions, and some umbellifers, which in time gave way to 
perennial grasses, docks, plantains, &c. 
In America, wherever Europeans had put their foot, there Dutch 
_ Clover had sprung up, while in South Africa, Australia, Tasmania, and 
New Zealand, the Scotch thistle, plantains, docks, &c., became noxious 
| weeds, though the thistle had been found the best agent in breaking up 
_ the soil and rendering it fit for cultivation, owing to its roots pene- 
: trating So deeply. 
y 
One strange fact had been noticed—our European annuals in New 
Zealand proved themselves superior to the perennials of the country ; 
thus, while few of the New Zealand indigenous plants were annuals, 
half the naturalized wild imports, to the number of 180, belonged 
to this class; while the dock, the sowthistle, and the white clover, 
D 
