378 
PECULIARITIES OF PLANT LIFE 
to man and his dependence upon them, there is another 
interest, — that of the scientist in plants as organisms. 
The scientist studies how plants are like animals; how 
they differ from them; how each is dependent upon the 
other for waste products; how plants depend upon animals 
for the pollination of their flowers and the scattering of 
their seeds and how the plants make use of the wind and 
water for the same purposes. 
He studies, too, the increasing complexity of plants 
from the simple, one-celled plants dependent upon water 
for existence, up through the plants which are becoming 
accustomed to living on land, and finally to those which 
have complex systems and complex flowers. He finds that 
all are related, and the more he learns about them, the 
more interesting does he find their relationships. He is 
interested in seeing how the change from water to land calls 
forth changes in structure to fit the new environment; how 
in land plants, each one has adapted itself in form, size, 
arrangement of leaves, and so on, to make the best possible 
use of the air and water which it is able to procure. 
In trying to find the causes of such variations of plants the 
scientist performs many experiments, often upon the smallest 
plant, for size and complexity are no indication of the 
interest which may center in a plant structure. Bacteria, 
for instance, which are the simplest and smallest of all 
plants, are being studied more to-day than any of the others. 
Every year adds to our knowledge of the nature of plants, 
their relations to one another and to man. Besides these 
relations due to their surroundings, plants bear towards 
one another the relation of dependence and independence, 
which we have discussed under parasitism and symbiosis. 
Plant life itself remains a mystery. The poet Tennyson 
has given expression to thoughts of those who have tried in 
vain to solve the many problems which have arisen in con¬ 
nection with the study of plant life. 
