A WORLD OF GARDENS 
103 
comes too severe for them. The highest place 
where trees can grow is called “timber line.” 
Above this point there are no trees. From here 
to the peak of the mountain the plants become 
smaller and smaller and more like the plants of 
the arctic regions. If the mountain is very high 
and the peak covered with snow all the year 
around, there will be no plants at all, as in the 
antarctic where there is always snow. 
The grasses are the most important family 
in the plant kingdom. They cover the earth. 
There are over one thousand different kinds of 
grasses and they grow in every climate where 
anything can grow at all. The largest grasses 
are the bamboos, which grow in hot countries; 
and the smallest are tiny plants no taller than 
moss which grows in very cold climates like Ice¬ 
land and Siberia. The world would be a much 
poorer place if it were not for grass. Indeed, it 
would be impossible for men to live at all. 
In the first place, the roots of grass form a 
network which binds the soil together. If they 
did not, the wind would be constantly blowing 
What is the most 
important family 
in the plant 
\ingdom? 
