284 
THE PLANT WORLD. 
first sends an immigrant moss (F unaria hygrometrica), to pre¬ 
pare the way for settlers. Later a few winged seeds or fruits 
lodge on the ground, spring up, flower and spread. By this time 
the soil is prepared to support more and more plants of higher 
organization. Soon the hitherto dreary waste becomes a literal 
flower garden. Here, cheek-by-jowl, may grow the rare exotic 
and the humble immigrant. Unseemly objects are by degrees 
obliterated. There results an incessant fight, a guerilla war¬ 
fare, an advance, a retreat, a victory or a disaster, a time of 
plenty or a famine, as the so-called “ improvement ” extends or 
recedes. 
Railroads are active factors in plant introduction by means of 
which they extend their range and even spread over a city or 
town. 
On the other hand, plants may yield to the ever-changing en¬ 
vironment, where filling-in and excavation, a dry or a wet con¬ 
dition, good soil or sterile ashes, alternate from year to year. 
In consequence we find extreme instability attending vegetable 
life in such situations. In the midst of a “ waste place,” where 
dump-carts deposit the disjecta of the city, there may still exist 
a swampy spot maintaining the usual lacustrine flora, consisting 
of cat-tails, arrow-heads, water-plantains, wild-rice, sedges and 
reed-grasses. 
As such a place becomes more and more filled in, the char¬ 
acteristic plants are bound to die. They possess no resources 
for withstanding semi-burial or even great dryness. 
Again we find plants on the arid parts of the waste to which 
immersion would mean death. The worst thing, however, with 
which any of them has to contend is the being overwhelmed by 
material thrown over them. 
It is thus a very interesting study to note from year to year 
what plants have newly arrived, what native ones still remain, 
and what immigrants succcessfully invade their ground. 
