44° ELEMENTS OF BOTANY. 
Perennial plants live for a series of years. Many kinds of 
trees last for centuries. 
The Californian giant redwoods, or 
Sequoias, which reach a height of over 300 feet under favor- 
able circumstances, live nearly 2000 years ; and some mon- 
Fic. 28.— Twigs and Branches 
of the River Birch. 
strous cypress trees found in Mexico 
were thought by Professor Asa Gray 
to be from 4000 to 6000 years old. 
67. Stemless Plants. — The so- 
called stemless plants, like the dande- 
lion, Fig. 29, and some violets, are 
not really stemless at all, but send 
out their leaves and flowers from a 
very short stem which hardly rises at 
all above the surface of the ground. 
Now, as will be shown later (§ 241) 
plants live subject to a very fierce 
competition among themselves and 
exposed to almost constant attacks 
from animals. 
Any plant which can grow in 
safety under the very feet of grazing 
animals will be especially likely to 
make its way in the world, since 
there are many places where it can 
flourish while ordinary plants would 
. be destroyed. The bitter, stemless 
dandelion, which is almost uneatable 
for most animals, unless cooked, 
which hes too near the earth to be fed 
upon by grazing animals, and which 
bears being trodden on with impu- 
nity, is a type of a large class of hardy weeds. 
And while plants with long stems find it to their account 
to reach up as far as possible into the sunlight, the cinquefoil, 
